Timing this room is hard so numbers might not be completely accurate, but the estimate I got from doing this strat compared to hugging the left wall was about 1s - 1.5s. Sometimes you can get hit by that last row of guys if you get a bad bounce which loses about 0.4s - 0.6s so it's still faster. If things go wrong or you mess up, then I was losing about up to 2s to my fastest times for both strats so there isn't much of a difference there. This strat seems to be more consistent though at least for me. Useful for any categories that want to quit out from this grub like grubsong%
I found this movement for the grub under sanctum, pretty consistently at or under 11 seconds for that room, best being 10.66 (I checked some 107 runs that get this grub entering sanctum and elowen had the cleanest at around 12 sec) and I think I've done it over a hundred times and only had the rava run into me once so it feels much cleaner than going right then up. the wall jump on the small ledge can be a bit awkward, but you can dash into it (but don't hold left until the dash, else you'll dash off it and it goes badly). also, because of the way you aggro the rava, even if you miss the pogo or walljump, you can safely climb the right wall. the two dashes after the grub can be a bit tight, i've found letting go of a direction during the second means i don't overshoot it and fall into the elevator but ymmv. not sure if it applies to other categories/patches (did this on 1578) but maybe? (also yes i should use hktimer i just didn't feel like setting that up today)