The script /etc/ppp/ip-up runs /etc/ppp/ip-up.local as the first thing it does, and then later on runs /etc/sysconfig/network-scripts/ifup-post. The problem with this is that /etc/resolv.conf doesn't get modified until the second of these scripts is run; so anything the user adds to /etc/ppp/ip-up.local can't do DNS lookups correctly (e.g. flushing mail queues may not work, etc.)
Changing component to initscripts, which supplies this file.
This will be fixed in initscripts-5.32-1; the local script will be run after ifup-post.