I think this is a case of Wikipedia being in a muddle (check the Talk page.) I can believe WDC were started in 1978, but I can also believe they had no branded product until 1982 or 1983 - they called themselves a design center, and they made designs. (These days they describe themselves as a fabless chip company, but the term was, I think, not in use at the time.)
So, it seems WDC might well have originated all the CMOS 6502 designs, and eventually did use foundries to make WDC-branded chips. Did they make a 65C02 before their 65816? I'm not at all sure. It seems that CMD and VTI (aka VLSI) made '816 chips, and I wouldn't be surprised if their chips - licensed from WDC - came well before WDC's own.
The thing is, selling licenses for a good CPU design to well-known chip makers could be a more assured route to a good market share than selling your own-branded CPU design.
Ref:
http://www.cpu-world.com/CPUs/65816/index.htmlI would think WDC never had any NMOS product.