Name of main process differs between servers (postmaster vs postgres)

Hi,

I noticed on two of my postgres servers, one has "postmaster" for the main
process, and the other has "postgres". My question is - why is this? For
example:

Server1:
postgres 909 1 0 May08 ? 00:03:55
/usr/pgsql-9.6/bin/postmaster -D /var/lib/pgsql/9.6/data/

Server2:
postgres 4804 1 0 May01 ? 00:05:08 /usr/pgsql-9.6/bin/postgres
-D /var/lib/pgsql/9.6/data

Both servers are running CentOS Linux release 7.4.1708 for the OS
and PostgreSQL 9.6.8 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5
20150623 (Red Hat 4.8.5-16), 64-bit.

The only differences I've been able to find so far are:

1) When doing a ps, server1 shows a trailing slash for the $PGDATA
directory whereas server2 doesn't have the trailing slash. I echoed $PGDATA
on both servers and they're both the same (no trailing slash).

2) Server2 has an additional package installed
-- postgresql96-contrib-9.6.8-1PGDG.rhel7.x86_64. Aside from that, both
servers have the same packages installed:

postgresql96-9.6.8-1PGDG.rhel7.x86_64
postgresql96-server-9.6.8-1PGDG.rhel7.x86_64
postgresql96-libs-9.6.8-1PGDG.rhel7.x86_64
postgresql96-pglogical-2.2.0-1.el7.x86_64

Looking at the documentation, it seems that postmaster is a deprecated
alias for the postgres process so while they differ in name, they're the
same in spirit?

From what I can tell, things are running fine on both servers, I guess I
just don't like there is a difference/inconsistency. Can anyone please
explain this?

Thanks!

Jon