If I'm not convinced enough, I will just move on with my current version till download completion, before updating to the newly released version.
Here's a convincing reproduction...I've restored a 1-month-old Bitcoin datadir backup and pointed Bitcoin Core v27.0 to it;
After a few minutes, I closed it before it fully sync:
After it gracefully shutdown, I opened v29.0 using the same datadir:
And as you can see, it just continued syncing without issues.
I just finished downloading the latest version but haven't installed it yet.
AFAIK, the most notable changes between those versions are related to "bind" setting if you have it in your bitcoin.conf file or command line arg.As well as the change in default datadir in Windows, but it will still prioritize the old datadir if it can find it there.
Custom datadir isn't affected by that change.