Some may think this is a minor issue, but when your phone is integrated into your work life and your clients are asking why you have notifications silenced, it becomes a more urgent problem to fix. Fingers crossed, I was finally able to fix this bug, but I'm still not entirely sure what did the trick. In addition to everything mentioned in this thread I also did the following: I continued switching settings on and off, on both devices around focus settings and messages, restarting the phone several times, upgraded to iOS16, I then did a soft reset (volume up, volume down and holding the side button until apple logo appeared), One thing I noticed under the default DND that cannot be deleted, under >Turn on Automatically, even though the DND was off and nothing was added under, "Turn On Automatically" the "Share focus Status" under the schedule box was greyed out but there was a checked box. (On the phone, this was before I upgraded now the settings are different), but on my Macbook Pro I had to add a schedule, then I could uncheck that box and then remove the schedule again. See image below.
I also enabled Messages in iCloud on my laptop (which is a new model) and synced. I have no idea which of these things finally did the trick.
After all of this, a week of troubleshooting on my own and with Apple Support, I'm very hesitant to use any kind of focus mode going forward which is unfortunate as the only one I used was for my sleep schedule and it was very nice not to hear text dings while trying to sleep. I guess I'll go back to using the side silent mode switch at night.