I sent a PR about this on Monday, and rather expected it to be fixed
by now (to minimise the number of bogus /dev directories people
generate using the current MAKEDEV scripts).

There's a simple error in the calculations in MAKEDEV for ptys that
causes it to generate minor numbers much bigger than they should be
(which should all still work if you start with a clean /dev before
using this MAKEDEV - but can cause duplicate minor numbers if you had
some ptys before & generate more, or more likely, if you generate some
with this script, and then more later after the problem is fixed).

See PR misc/15650  (I had no idea what category errors in scripts like
this should be filed ...) for the details and the fix (which is truly
trivial, though it does need to be applied to a lot of MAKEDEV scripts).

kre

ps: this has nothing at all do do with problems that would be caused if
new ptys are not listed in /etc/ttys...