Possibly caused by MC-268543.
The bug
All armor trim textures are compiled into an atlas when loading resources. For some reason, armor trim textures with specified animations do not become animated, unlike what is the case for every other type of texture which is added to an atlas.
How to reproduce
A resource pack that gives dirt and the coast trim the exact same texture with the exact same animation specifications is attached to this ticket.
Download and apply
Look at dirt
Look at something trimmed with Coast
Expected results
Both are animated.
Actual results
Only dirt is animated.
Linked issues
duplicates 1
Attachments
Comments 2
It seems that armor trims do actually support animations and that the reason they don't show up here is because of MC-268543, so this can be closed as a duplicate.
Can confirm.