There's also shotadom and muscular_shota. All three tags seem to be pet tags of user #723815.
Hmm I'll take responsibility for shota on shota and shotadom but I didn't make the muscular shota tag.
I suppose the child_on_child yaoi would be fine. The idea was to make the search easier for people looking for that specific content instead of using two tags they could just use one.
As for it added to safe posts, onee-shota is added to safe posts.. so I'm not sure I see the issue with that.
Two shotas could just be kissing or be implied romantically without it being explicit.
Also as Unbreakable said there's a lolidom and a femdom. I don't see why shotadom shouldn't exist.
All in all, I do think there's a place for all three tags. However, it's not that much of a hassle for a member to do a two tag search. Child in child yaoi is good. I guess
Now about nuking muscular shota I think it would be good to have it renamed as muscular_child, as Damian suggested. While I do agree it doesn't come up often there are muscular_children that show up in Shonen works.
Trunks and Goten for example which are my first thoughts.
Killua has been drawn to be very muscular and we do have muscular male and muscular female so muscular child should be alright.
Anyway, I had my say on the matter. I came up with those tags because I thought it would be helpful. If the judgements is that they aren't that good or helpful then I'm fine with the decision to nuke.