Idk?
Why can't you analyze games of 3-check?

Import your games to another site that does this and analyze them there.
Or just chat with @TenThousandDays - you seem like the chess 3+ expert on chess.com to me Lots of 3+ articles on chess.com that @TenThousandDays has posted too.
I don't play 3+ much, but maybe chess.com will add analysis feature for this variant and others in the future (but I'm not going to hold my breath either), but some newer things are on the horizon (I'm part of chess.com beta club and we test out newer features before they come out).

Import your games to another site that does this and analyze them there.
Or just chat with @TenThousandDays - you seem like the chess 3+ expert on chess.com to me Lots of 3+ articles on chess.com that @TenThousandDays has posted too.
I don't play 3+ much, but maybe chess.com will add analysis feature for this variant and others in the future (but I'm not going to hold my breath either), but some newer things are on the horizon (I'm part of chess.com beta club and we test out newer features before they come out).
Yeah I know a thing or two about 3 Check.
It is kind of strange how chess.com has neglected variants so far. The stats for variants are non-existent as well.

because in three check, (which I play quite a bit) it's a good move to sacrifice your queen to just check (here is an example) this confuses the engine
If you use a standard chess engine then yes it will say that this is losing for Black but if you use a 3 Check engine then it will say Black has forced mate.
The title says it all.