Sorry, this is getting confusing a little:

This person looks like a mistake:
https://hkmdb.com/db/people/view.mhtml? ... ay_set=eng
QUADRALS credits say 石健, not 石建丁.

石健 exists, no writing credits though:
https://hkmdb.com/db/people/view.mhtml? ... ay_set=eng

But there's also a 石健丁 (健 instad of 建):
https://hkmdb.com/db/people/view.mhtml? ... ay_set=eng
石健丁 is listed as director in DUEL AT BLACK DUNES, which looks like a mistake, too.
According credits he had a different job, something with 導, but not 導演, maybe 指導 or 副導, I can't read it clearly:

石健 was actor in the same movie. Maybe the same person? And maybe the writer of QUADRALS?

The official HKMDB language expert and I went thru the Duel at Black Dunes credits frame by frame and see that 石健丁 is actually credited as 助導 (a shortened version of assistant director). So 石健丁 is incorrectly credited as a director (as you point out). And of course 石健 is credited as an actor (who has three directorial credits).

Anyway, I (we) will do some more digging to see if this is possibly the same person. It seems quite possible.

Again, nice work digging this up, C.