The unkind world we live in would see this role being abused quickly and a person not lasting long in this role. For one, in the wrong team, it might lead to devs just doing 80% of the work and leaving the rest to the janitor. And the janitor might get fed up with having to fix the buggy code of their colleagues.

I wonder if the janitor role could be rotated weekly or so? Then everyone could also reap the benefits of this role too, I can imagine this being a good thing for anyone in terms of motivation. Fixing stuff triggers a different positive response than building stuff