Definitely true, but Gaylord Perry won 20+ games that year, and wins were a thing that mattered way more back then than they do now. Swan didn't even finish top ten in voting! And there were five guys with better ERAs than Perry. But, there were also 13 guys separated by half a run of ERA. As it stands right now, deGrom is about seven-tenths of a run better than Nola, and only Nola and Scherzer have been within an entire run of deGrom.
deGrom has an easy lead in fWAR, passed Scherzer and moved into second in bWAR, and blew past Nola and is neck-and-neck with Scherzer in WARP. He's substantially ahead of those guys in FIP and xFIP, gives up fewer homers and fewer walks. Only Scherzer (and Corbin by the slimmest margins) have a better K/9.
Literally the only reason I could see voting for any of the other guys is because you really value win. Or, you care that their teams were nominally in playoff contention.