When I play a solo I'm not using the volume of the guitar. I ignite a boost after the stack.
If you play with medium or high gain, a little more gain from the guitar's volumeknob does not make you cut the mix.
Absolutely, if you have a lot of gain to start with the sound is so compressed that nothing in front of the amp will change volume. I still ride the volume knob for varying the sound quality (tone and cleaning up etc) but it definitely won’t provide a solo boost. Most of the time I am using more mid gain type tones though
Another good point that was made earlier in the thread though was about band dynamics. Quite often a solo doesn’t need much boost if other band members are sensitive to overall dynamics and create a little space for the solo instrument.
As always there is no single right o wrong way just what works for each individual.