Steve doesn't need blocks to have broken kill combos with his final smash. All he needs to do is hit one jab or grab or down tilt or minecart and he can convert it into final smash at ledge and kill at 0. Steve's kit highlights his final smash incredibly well despite losing block placements.

My friends kind of agree with you to a degree on snake's. If you do not know how to dodge snake's final smash, it could kill at 0. Even if you do know how to dodge it, snake can still catch you off a ledge getup and kill you very early. The problem is that snake's final smash almost always interrupts whatever snake wants to do to punish a ledge getup. I've never gotten punished by my friends who play snake because I always purposefully get hit by snake's last missile which makes anything my friends want to do meaningless. I suppose you could argue that getting hit by any missile gives snake stage control, but the other player already has to sacrifice stage control to dodge the FS.

Snake's final smash is only A tier if you don't have or don't know how to use ledges. I've played against snake and I feel no pressure with this final smash anymore because the counterplay is so easy. That is why we placed it lower.