No idea if its true or how it works but ive heard that said about string instruments like violin/cello type instruments.
I imagine the theremin sort of requires this in its way as well.
As opposed to something with buttons or physical quanta that predetermine the sound that is possible from engaging them as known without need to finetune or ise ones ear to get it right
Stringed instruments with a fingerboard require the player to develop the skill we call “intonation”, unless the fingerboard has frets.
Brass instruments require the player to develop intonation via their embouchure. They literally buzz the notes with their lips.
Reed and woodwind instruments require embouchure but the embouchure stays consistent across notes (although some changes can bend, overblow, or change octaves). That said, the player can change the pitch a little with their voicing, but the real note changes are discrete valves (like keys on a piano).