I have made a comment previously on Yomi Counters activating on the frame that the grab lands. However, there are some gameplay considerations to take into account. One specifically is fuzzy guarding. Currently, it is very possible to fuzzy guard against a throw and then another option that the opponent would have because you are able to delay your inputs for the required number of frames for the startup of a certain attack. This delay will guarantee a Yomi Counter against a throw that would have come out sooner. If we only require an extra frame or two of no input, then it would make fuzzy guarding more difficult. If we require more than those extra frames, then fuzzy guarding may become non-existent.
As it is, I like fuzzy guarding options because it opens up more layers of depth. So, I think I am against my previous comment (which I made before I actually started to play and realized that fuzzy guarding against throws was possible and is very fun).
Edit: Just realized something, a possible solution would be to have directional throws require extra frames of no input to Yomi Counter… but this may confuse new players unnecessarily. So, my first feeling is against this solution. Although it would be even more incentive to leave neutral for throwing thus reducing accidental Yomi Counters beyond the one frame advantage now.