I just gave this a shot and it seems OK to me - it is quite a bit later than originally posted. We think it might have been a bug at the point in time you mentioned it that got fixed later.
To reproduce, I tried:
curl --header "Authorization: Bearer $ASANA_PERSONAL_ACCESS_TOKEN" \
--header "Asana-Fast-Api: true" \
and got back 10 results from projects in the workspace I supplied.
Let us know if this didn’t actually test the scenario you were talking about!