That explanation is consistent with my observations. If I reboot, instead of pausing on striped bars, the screen will show the safe to turn off screen. If I turn on the SE/30 a few seconds after turning if off, the safe to turn off screen will still show, but with a handful of pixels that are incorrect.

One thing I noticed, is the initial pattern that appears might depend on the rev of board. Another board shows the more typical wavy vertical lines at boot with a non-stock ROM.