If anyone stumbles across this in the future, this described behavior is now supported as of 1.21.9-pre1
Additional screenshots of behavior:
Relevant decompiled code:
To make use of the second horn, one of these should be .texOffs(0, 40) rather than .texOffs(0, 32)
.texOffs(0, 40)
.texOffs(0, 32)
If anyone stumbles across this in the future, this described behavior is now supported as of 1.21.9-pre1