Further testing reveals it’s directly related to the default pregain saved for a channel. EVEN if you overide this and set the channel pregain back to 0, before rendering, and set the rendered channel pregain to 0 too.
I discovered this doing the invert phase test and boosted the channel until cancelled, showing me my rendered channel is 14.4db quieter, which happens to be the exact same amount set for the default channel preset.
is this normal or a bug? I can’t remember!