Hello Filet-o-Fish,
Thanks for posting in the Apple Support Communities.
It sounds like Freeform isn't syncing completely between an iPhone and your Mac Pro, right?
If we have that correct, you've taken some great steps to isolate this already, and we appreciate these details. Let's see if this may be occurring due to Low Power Mode being enabled on your iPhone. If this is enabled, syncing services may be disabled until the battery is charged or Low Power Mode is disabled.
For assistance with disabling Low Power Mode to test this, check out the following resource. We'll include details from the resource below to help out: Use Low Power Mode to save battery life on your iPhone or iPad - Apple Support
To turn Low Power Mode on or off, go to Settings > Battery. You can also turn Low Power Mode on and off from Control Center. Go to Settings > Control Center > Customize Controls, then select Low Power Mode to add it to Control Center.
When Low Power Mode is on, your iPhone or iPad will last longer before you need to charge it, but some features might take longer to update or complete. Also, some tasks might not work until you turn off Low Power Mode, or until you charge your iPhone or iPad to 80% or higher.
If that doesn't appear to be related to what's occurring, contact Apple Support directly to check into this with you in more detail.
Have a great day!