It's guaranteed guys. DIing behind away in whatever direction (including holding up + behind, up + down) can be followed. It cannot be airdodged or jumped out of, it's 100 guaranteed. DI can be reacted to, but it's harder than other throw Uair combos. I tested it on Mario but I have tried it in matches against Roy, Peach, Mewtwo, Robin, Kirby, Bowser and Bayonetta. It worked flawlessly on every character but Bayonetta. Vs Bayonetta execution is much tighter. I did get it sometimes, but at times she was able to Bat Within which is on frame 1. I'm quite sure it's guaranteed on her too though, but just a bit harder (also note she has the laggiest airdodge in the game so if you bait it you can kick her or whatever). Then again the characters I tested the Dthrow Uair on all had frame 3 airdodges instead of frame 2 airdodges except for Mewtwo, and I'm quite sure it doesn't make that much of a difference.
One important thing to note is that Dthrow has a base knockback value of 80 whereas Uair only has 30. As we all know, moves with higher base knockback have a bigger rage effect so this means that rage affects Dthrow more than it does Uair. As a consequence, at kill percent with rage Dthrow will pop them up too high for Uair at connect (and when Dthrow Uair does connect atbrage percent, it will likely not kill because Uairs rage effect is not big enough). In order for Uair to connect at rage percent, it seems you will have to double jump. It will catch every optiom except for airdodge. This means that with rage Dthrow becomes a 50/50. I have tested very little with rage however since I didn't have enough time so this requires much more testing.
In summary:
Dthrow Uair is guaranteed, regardless of what character.
The window is tight.
DI can be reacted to.
With rage it likely becomes a 50/50 but this needs more testing.
