The problems with it being a guaranteed successful grab from just starting the grab animation is that
a. this can happen at inconvenient places where some preferred camera angles can be obstructed with walls or objects like furniture, high piles of trash etc,
b. maybe you want to be grabbed by a specific simp type at the moment for any reason, like gangbang combination or that many different simp types have their specific sex animations.
This becomes much more difficult because they start their grabbing animation when they're close enough to trigger it and there's no way to avoid it other than going out of your way to keep away. It was much better and convenient to be able to lead them where you wanted even if they got too close by dodging, and then let yourself get grabbed by the simp you want, instead of worrying about the one that triggers it's grab earlier than others.
Maybe it's unintentional but the result is unnecessary player restriction. You said yourself it's for fap only. It's like having a gallery mode only you don't choose in what order which enemy you get to see sex MC or which place.
Devs can fix this by simply making you ungrabbable during dodgeroll again, and make it easier by bringing back the slowmo reaction event in H mode if someone tried to grab you. That's all. Revert these 2 things. If you want very fast sex, you could always just grab anyone yourself.
Also the fact that some simps are very fast or have ranged attacks like the spitters makes it all very tricky in normal mode
