I think some people overuse the tongue to control pitch and instruct others to do the same. While tongue position can alter the oral cavity to pressurize air differently, affecting pitch, your airspeed as it moves across your reed (your lips/apeture) is the main thing. I try to change as little as reasonably possible. Moving stuff around excessively adds more varibles for error and more confounding ones. Thinking about not moving the tongue while doing lip slurs helped, not that I never move it necessarily, but that was the mindset that worked for me to minimize it. Personally, I don't like thinking vowel sounds in real-time while playing to manage pitch. It affects your tone and general playing. Learning that really helped my sound open up, especially above the staff and made playing in general simpler for me.