yeah, i guess the “stop” isn’t processed until after the note on event. so some voltage hits your speakers. maybe all effect commands work this way, i have never really thought about it. setting volume to zero works as expected though.
0x00 is not “mute” but stop all currently playing notes and effects. If you don’t want that click, simply combine with the 0L00 command or set the volume-column value of the note to 00.
Renoise seems to need 180 samples before the 0x00 effect really kicks in, where the 0L00 is directly applied, so i guess 0x00 was not designed to be applied on songplay or it is a side-effect of a fix where the first notes aren’t being played when Renoise is triggered to render.