Thoughts on the hippopotamus defence?

This defenses around the Hippopotamus and the Hedgehog IMO are advanced concepts.

It's easy to slot the pieces into standard positions in these defense. But.... if you don't understand the concepts all you are doing is giving White a space advantage to whip up an attack. To play these defense well you must understand what White's back rank is doing, where the break through is likely to happen. That's not easy when your a novice. Also... these defenses' pawn formations tend to be mobile.. after one move. a chain of events can cause the whole pawn formation to change...

It is no good as a "catch-all" Defense. It is only effective really against one line where White commits to a4 and does not go Austrian.

1.e4 g6 2.d4 Bg7 3.Nc3 d6 4.Nf3 a6 5.a4 - only here, where a4 is played AND the Austrian Attack is avoided, is it a legit Defense. If instead, something like 4.f4, or 5.Be3, Black needs to act far quicker with moves like b5 and c5, not the Hippo.