Shears of Winter should have the following tags added:

1.20.1:
minecraft:tools
forge:shears
forge:tools/shears

1.21.1:
c:tools
c:tools/shear

Just added these in 1.21, I don't really maintain 1.20 other than critical fixes and as this is the only comment regarding these tags for that version I don't see that as critical. So I am going to close with the 1.21 addition, but if you know of some bad issue / incompatibility these missing tags are causing in 1.20 feel free to add this info in here and reopen

1.21.1 only is great, only has 1.20.1 there because when I made this issue that was the maintained version.