Madara absorbed a Senjutsu-Rasenshuriken before.I get the feeling Momoshiki was using Senjutsu with that attack. I don't think Preta Path can absorb Senjutsu. Either that or Sauce was Nerfed as others mentioned. I'm still waiting for Sasuke to use Shinra Tensei or Chibaku Tensei. We know he has Chibaku Tensei. Why didn't he use that either?....yeah I'm gonna go with Nerfed
It's just that the Rinnegan-user must be able to control Senchakra, that's why the one Pain-body became a frog-thing when he absorbed Narutos Senchakra directly. Sasuke should be able to control Senchakra, considering that he had a pseudo-sagemode with his cursed seal for years.
After all, we don't know if Momoshiki used Senjutsu, but I doubt it. Weren't the rocks that burned Sasuke just heated rocks? If yes, then there was no chakra to absorb in the first place.