Huh, I just checked stats on ecosyste.ms It looks they consider as maintainer only those people who listed on package.json, not a real number of contributors on github or anything. So all conclusions in this post is based on wrong assumption and incorrect data interpretation. That's all you need to know about it. I think you could list random people on github in your package.json to looks cool in eyes of stats cultis…
Maintainers and contributors have overlapping but subtly different responsibilities AFAIK. Maintainers are the ones responsible in the end for the state of the repo while contributors suggest changes.
So definitions does not matter when stats that author refers, does not include a developers who own over 50% code in repo, but includes me as contributor.
That's widely known problem of programmers to believe that world is perfect and all data are always actual. Actually it won't.