They did recently add the ability to view the results of the assistant’s search i.e. the full chunks returned from the vector store. See here.
This is still far from satisfactory though as the chunks are often far too big to use as citations and it’s also not always necessarily the case that the top ranked chunk will be where the assistant ultimately draws its answer from.
A direct quote or quotes is pretty essential for any RAG application. Hopefully they add this soon.