Yep - as stated, if people are holding the trigger and the marker is firing, then that isn't PSP ramping, and isn't PSP legal. It's NXL mode, which is an entirely different thing all together.
Newer Shockers with the '09 tournament board would have both PSP ramping and NXL mode, as well as semi auto, Millennium mode and ramping.
Prior to that, Shockers had the Nerve board, which had semi or ramping, with four ramp activation rates. The ramp mode was not specifically PSP ramping, but was PSP legal.
The earliest Shocker boards were semi auto only.
Some Shockers would have come with "Team" boards. These gave semi, ramping or auto, with a wider range of ramp activation rates than the Nerve board. The full auto mode could be set up to provide NXL Auto mode.