bath bombs used to be the only way to get glass but with the addition of the grotto plus the CC fight they have become nearly useless due to their crafting cost and having to wait to mining the hot springs. They already have chances of dropping blue and red gems (like if we need more blue and red gems sources) so why no add all gems? atleast will make them a niche way of getting extra gems since the only ways to get gems are killing fw to reset the ruins (low % of player do this even with the automatic farm via cheesing him) or dragonfly
new players will have a way to get gems in a pacific way and veterans can break the routine when comes to farm gems or get extra if some high gem cost big building is planned
in addition it will have sense lore wise since wormwood is made by a green gem from the moon and in the metheus puzzle (was from metheus puzzle?) murals we can see that there is gems in the caves because the ancients took them from the surface to the deeps