I've been building my own version of the STRPDM menu so that the System Name and additional options appear on it. (I've never liked the PDM menu itself.)
As I was browsing the CHGPDMDFT (Change PDM Defaults) command (by the way, I didn't even know it existed until this week when I ran GO CMDPDM) I saw it contains a DSPINFMSG parameter.
By setting this parameter to *NO, you no longer receives those annoying "Please use the modern alternative to PDM because we really feel silly providing SEU in 2014" messages.
You can also get to this option by press Shift+F6 and then PageDown, then change the "Display informational messages" entry to N.
Here's the command:
CHGPDMDFT USER( usrprf ) DSPINFMSG(*NO)
Sadly, the USER parameter does not support USER(*CURRENT). But hey, they haven't updated PDM in a decade.