Alright, continuing to research this. So yeah, getting a better handle on the ini file structure, the line entries are in the order of your own personal ports (which is why your line doesn't work for me). RGB sets of ports are one entry. So key section for me would be here:
...and those are (should be) controlled by this part of the line, that's propagating correctly from DOF Tool:
The first blink there is the fire button (working), followed by exit (not), how to play (not), start (not)...
Finally figured out what's going on. It appears to be a DOF Configtool bug. For whatever reason, on only the pinballx line (when it appears to be working right for everything else?), it is making only one entry for the RGB Fire Button, causing everything else to shift up two entries. Those first two 'plain' ONs are going to the green and blue channels of the fire button, and the start button assignment is then seen as the exit... apparently. After a little bit of jiggery-pokery, adding in two more entries freehand into the line solves the issue, like so (with a little bit of experimental rainbow phasing on the fire button for good measure):
Which in turn leads to:
(blinking start and launch not apparent, but working)
Good news is, I guess it really wasn't on PBX end! Obscure DOF Configtool bug, apparently? Bad news is, I need to save that line and updating table definitions is now less trivial, until I find who to report that to...
Thanks!