From what I am seeing it would appear that PMK format was virtually written off but in AC24 it seems to quite readily accept the Published AC24 PMK format and even allows for exploding but trying to import a file from 2003 caused a crash. Looks like I will have to use DWG for now.
If GS are trying to restore PMK as a working 2D format in AC then perhaps a review of reading legacy PMK files might be worthy of a bit more attention. At least that would elevate the format to be more in line with DWG and PDF.
Apple iMac macOS Ventura / AC26UKI (most recent builds)