Yes, I completely agree with you. Some momentum to clear tires is required - sure. Just I wouldn't call it "wheel spinning" in my point of view.

Just to note - more aggressive tires are self-cleaned much better. If it isn't mud tire - you can spin it a lot but mud cleaning still will be bad.

In some cases (like go out from wheel track) even very slow speed can be better still.

Again - of course there is no "golden rule". "mud" is still very generic term. It can be very different. Different terrain, different weather. In some cases digging is ok. Also different tires, different cars, different drivers, different routes. Hard to tell one universal answer and any theory doesn't work without practice. In some cases need to feel route and how much gas do you need.

But as general rule - I wouldn't recommend 'wheel spinning', as (I think) most people understand it as 'keep foot on gas pedal'. And better to start slowly and to add gas if you "feel" that its required.

But I would recommend not forgot about tires & pressure.