Thanks for the quick reply @darthShadow. Curious what the implications of a very short directory cache expiration would be?
Testing --dir-cache-time=1s worked a treat. After the 5s delay from vfs cache: queuing for upload in 5s the file shows up.
From Dir-cache-time vs poll-interval I see the concern about a very low poll interval but from a bit of search I can't see if there are the same for a very low directory cache expiration.