Oh now I understand: its to match all 200 HTTP codes like 201, 202, 203 etc.
Because all 2xx responses are success; for simple (not Range or other special request scenarios) GET/HEAD it probably matters less in practice than for PUT/POST/DELETE, but 203 and 205 (and 204 for an existing but empty resource) are still possibilities.
I guess so it accepts all 2xx codes and not just 200?
204 satisfies the first check but not the second.
If you intend to do anything with the response you'd probably handle 204 differently otherwise you'll get the world famous null pointer.