Sure, there are those who purposefully attempt to hide or obscure their finances during their separation. They’re the scourge of family law, and don’t usually get away with it.
But when it’s alleged that you failed to provide financial disclosure, it’s implied that you can’t be trusted. That you must be hiding something. It’s the easiest argument to make, because it focuses the conversation on you, and relies on the old ‘absence of evidence as evidence of absence’ argument.
And it’s made all the time, in and out of court.