yes they record as if they are midi controls in the event list but they do alter the volume of audio tracks
that's how i muted a part of a track and that definitely carried over to a merged stereo file although rendering individual tracks the volume changes didn't work - that was the subject of the OP.
i discovered that volume nodes can be tricky. if you just add a node at the level you want, RB fades down over the whole track from the previous level. instead of muting where you want, it fades down slowly from the previous setting.
if you want bar 4 of a track to mute, you set a node at the existing volume on bar 3, beat 3 , 119 ppq depending on yuor resolution, and the node for the volume you want - zero for mute - at bar 4, beat 1, 0 ppq. same with restoring the level. if you don't set another zero node, the part will fade up to the new node at the desired level.