Some lemmas about commutative squares.

I thought these would be used in more places, but I only found one.
Is there any reason to prefer this version over the one that says `IsEquiv f -> IsEquiv g -> f == h o g -> IsEquiv h`?  That is, why do we care that our equivalence is `k o f` and that it came from `IsEquiv k` and `IsEquiv f`, rather than just having an arbitrary function?