As I understand it should, but I can't find any explicit statement. This is important for me because I'm trying to understand which MacBook should I use - with external GPU or not. Still I can assume that the answer to the question is yes because Apple sells 15-inch with external GPU while 13-inch without it.
UPDATE: In discussion bellow I found that my original question was wrong (also the wrong term was used - external, I meant discrete). I believed that OS resolution is an absolute setting for all applications. Now I assume that some functions work with native resolution, so it's obvious why they work slower on higher resolution.
Example of scaling to native resolution: https://developer.mozilla.org/en-US/docs/Web/API/Window/devicePixelRatio