The two things are completely separate. AIX supports both the AT&T and BSD standards for pseudo-terminals, with AT&T being the default.
You can change each number independently. Changes take effect immediately, without a reboot or even a need to log off and on again.
Have a read of the pty files page http://www.unet.univie.ac.at/aix/files/aixfiles/pty.htm
which seems to cover most of the details.