I like the "semantic" angle that York presents here -- that the donor could be a Democrat who donates to both parties, just as many wealthy donors do.  It wouldn't be the first time the NYT wasn't a reliable source when it comes to Trump.  OR it could simply be a lie.  And/or it could be a lie started by Deep State operatives.  Maybe players in the US Intelligence Community used Fusion GPS as a front to try to smear Trump on Clinton's/Democrats' behalf. 

In any case "wealthy Republican donor" could just be an attempt to deflect from or mitigate Democrats' involvement in underwriting the discredited dossier.  After all, the Russian Narrative was initially cooked up by Brent Budowsky and campaign chairman John Podesta in December 2015 (according to a Podesta email published by Wikileaks).  The book "Shattered", written by Clinton supporters, also mentions Podesta's and Mook's post-election plan to save face for the colossal loss by pushing the Russian Narrative.