Bad, it would make the move useless since it's needed to beat tracking moves, and it's the one universal move for everyone that can cause a fatal stun since some characters like Kula don't possess a unique one, or they're like Momiji where they're situational since her unique one is slow and only possible from BT. Making it a normal stun would demote it to only really being a strike when used after a wall splat, and some characters have fatal rushes that aren't suited for that situation due to their hit levels
And technically not all fatal rushes are four strikes, some characters like Helena and Phase, Christie, etc. have fatal stuns with multiple hits to keep there combo count toned down from the 30 hit limit since either they have amazing utility or have some special benefit like Helena being able to free cancel into one of her stances, Nyo entering her flight stance etc.
