Not GP but there is a consequence. These days if someone has used version control they almost certainly know Git.
That means pretty much everyone who comes in the door needs Mercurial training, whether formal or informal. You’d get the same effect from still using CVS, SVN, or other things.
That may not be a big issue. If someone understands version control I’d hope they could adapt to another minder pretty fast.
It’s still an issue. There is technically a cost.
There is an initial cost to learning hg, but it is usually offset by the less destructive nature of hg's behaviors and defaults in the long term.