macOS 10.14.3 Update can't be installed on this disk...

I have to admit that it's a very strange way apple changed the way with the combo update. Not sure if the message such as: "volume does not meet the requirements of 10.14.3" is the best way to tell the customer use the updater instead of combo updater.

Where are you located? 10.14.3 was available through Software Update yesterday. I updated 5 Macs using it.

The last I heard, Apple fixed it and the full installer now works. But I don't know for sure.

Reminds me of the original Mojave installation fiasco that had to be fixed with Terminal commands to get rid of legacy files, just to get the install to go through. No thanks. Apple never did admit to, or post a patch to fix, that problem. That was fixed by users of this forum.

I updated to 10.14.3 today using System Preferences > Software Update and it went through. But, it completely disabled my Bluetooth, which knocked out my wireless mouse and keyboard. I had to locate a USB mouse and keyboard to fix the problem, which wound up involving an SMC reset (a PRAM reset did not help).

I'm glad you didn't have the original Mojave installation fiasco happen to you. I lost an entire weekend because the installer completely hosed my MacBook Pro, and I wasn't alone. I have been using Mac's since 1993, and only posted this because the current updater to 10.14.3 seems to be acting a little odd, and if someone else had this problem, here is a way to get out of it.

You do need a mouse and keyboard to search the Internet forums for a solution to a computer problem. Jumping to resetting an SMC is not my first remedy of choice, nor are the instructions for doing so immediately available.

Bless your heart. Perhaps it is easier to plug in the equipment and use a 27 inch screen and full size keyboard, than it is to try to search on a little dinky screen and type on a little dinky screen keyboard and read little dinky instructions. Despite all the advancements in the iPhones and tablets, internet searching is still a pain on them. (Yes, I have an iPhone and iPad.)

I know, it's sad but I have no use for a smart phone. On the other hand I do have 4 iPads up to a 12.9" Pro. I don't have any problem searching on the smallest iPad screens but that doesn't mean everyone shouldn't.

I have 3 iPads up to the 11" Pro. Love 'em. Use them all the time. But sometimes web sites don't work right on them, and links and buttons won't work (especially things built with Flash or with panes that don't activate), etc.

The point of the whole original posting is, my Bluetooth got knocked out by the update. My iMac came equipped with a wireless magic keyboard and mouse (both Bluetooth). I really wanted to get them going again, so I could use the iMac with its equipment. Bluetooth would not reappear with restarts and NVRAM reset. To get the Bluetooth going again required an SMC reset. Yes, now that I am not so flustered and have thought about it, this can be done by unplugging the iMac for 15 seconds. However one chooses to make it happen (keystrokes and power buttons, or pulling power plugs), getting the Bluetooth back required an SMC reset. OK? We good?

In my case I tried the combo only when the Software Update failed inexplicably. ("Installation Failed An error occurred while installing the selected updates." Several search hits suggested the combo updater might be a way around the stuck state of the Software Update.

So now it's in some odd state where it can't download the update (again) and doesn't like the update and the combo updater says it can't be installed on this disk.

Standard MBP late 2017 4 TB ports 512 SSD. (AP0512J) Disk Utility says APFS Volume APFS (Encrypted).

Machine purchased just prior to Mojave and has accepted Mojave and subsequent updates fine. Until today.

System Preferences> Software Update only works if your Mac is running Mojave on an SSD formatted as APFS.

That is not true.

Mojave and Software Update are fully supported on Macs with normal hard drives or Fusion drives.

The delta update is the update that upgrades from 10.14.2 to 10.14.3.

The combo update will update from any previous version of Mojave to 10.14.3.

The combo update install has been recommended at times to fix issues that may have been caused by the application of previous updates.

Mojave converted my SSD drive in my laptop to APFS, but has not yet converted the fusion drive in my iMac which is still running HFS+ even after several Mojave updates.

I'm actually surprised by that; every source I've read says that all boot drives - including Fusion and spinning hard drives - are converted to APFS by the Mojave installer.

Just that when Mojave came out I was unable to install it through the App Store for the reasons mention in my original post, I had to copy the Mojave installer to my MacBook Pro and use target disk mode to install it in the iMac 27. I used the same process to install it on the MacBook Pro.

Yes. You've mentioned that three times now. And I'm still not sure why you are telling me. But since the third time's a charm, there had to be some reason you had to go to such measures that was local to your Macs.