One kind of freeze in particular is intentional – when a super flash occurs, many games will pause for a few frames, with neither player being able to move.
During this period, few games will register command input from either player. The one who activated the super special move will often have complete invincibility, so this is implemented as a sort of stun from the activation until the super flash, maybe even allowing the opponent a miniscule chance to retaliate or defend.
The time taken by the freeze definitely depends on the game, and perhaps depends on the move.
There are moves that blocking or otherwise evading cannot be in time for after one sees the super flash; either the attack hitbox for these moves starts up at the very same moment of the freeze, or the defender (for whatever reason) has a longer freeze time.