I don't know the legality of disregarding instructions at a Class
G airfield (I thought that if it has an
ATZ and ATC then the ATCO can issue orders within the ATZ) but unfortunately the OHJ has been brought into some disrepute by a number of A/Gs or FISOs who overly enjoy their perceived power and order arriving pilots to use the OHJ even when there is zero traffic, and (upon query) the man admits he has no known traffic
Panshanger comes to mind, though it is years since I last went there.
I usually intercept the extended runway centreline and join on a long final, unless there is traffic.