When I went through Shawbury in the late '80s we were forbidden from doing any FW flying whilst on RW training, even as Crewman.
The reason given was that FW pilots may have subconcious reactions to a situation and would apply the wrong control inputs, mixing the two until the RW inputs were firmly implanted.
On my first weekend one of the guys on the course ahead grabbed me for a flight around the various nominated confined areas to prepare for his exam and solo signoff, (we hired a lovely C150 from Sleap) as I didn't offically start flying training until the Monday......