I've been searching for an answer to this but I can't seem to find a clear yes or no if this is supported.

It seems like a feature that's supported and it works perfectly fine in the Spine Editor, but when it comes to implementing it into the engine, it crashes on build.

I have a character with a few strands of hair, the hair is built with long meshes with a few bones rigged to each strand. I made an image sequence of the lock of hair with a highlight that sweeps along the length of the hair.

The character imports fine if the hair is using a static PNG texture but as soon as I make it an image sequence with the highlight that animates, the game won't build and crashes when trying to load Mesh Attachment Hair_Sequence.

I've done a few tests:
Rigged Mesh Hair with a static texture works.
Image plane with the animated hair sequence works.
Image plane attached to a bone with animated hair sequence works.
Rigged Mesh Hair with the image sequence as a texture fails.