glowstone stairs/slabs also can't be used to charge a respawn anchor, but each block is worth a non-standard amount of glowstone, so that might be intentional

coloured glowstone seems like it should be able to charge anchors

This is a valid bug, however dyed glowstone is likely going to be removed from the mod in the next update. Until then I'll leave the issue open.

Closing this as fixed; after removing dyed glowstone we added a block set for regular glowstone, and those blocks now charge respawn anchors