Honestly, there's not much to be said on this.
In Stormblood, the conscious and right decision was made to have tank stances remain persistant even when ilvl synching. This was a change that everyone liked!
For some reason, this change was not applied to tank stances when they were changed in 5.0; now tanks are back to forgetting their Shield Oats at the start of dungeons, and while it's a simple fix to just remember and turn it on, after an entire expansion of having a good quality of life here, there's no reason at all not to see that same quality of life reverted in Shadowbringers.
Return persistence through levelsynching for tank stances, please.