But i could certainly imagine a layout where breakign against c4 woudl actually be much better.
Agreed, that's why I said "Not entirely true" instead of saying "Wrong".
There's a line in the French 3. Nd2 variation where breaking against White's e5-Pawn by ... f6 is perfectly playable for Black, for instance.
... but lines like that are the exception, rather than the rule.
Not entirely true.
Certain pawn breaks are "indicated" by the layout of the Pawns. For example, if your opponent (Black) has a chain of immobilized Pawns stretching from f7 to c4, you could in theory break against either e6 or c4... but f2-f4-f5 breaking against e6 is indicated. The break against c4 is a positional error.