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
While it’s not to the same degree as a string instrument, a lot of brass instruments require the player to create the pitch. They might have 3 keys with which to play all their notes, so the sounds aren’t predetermined, they need to be pitched by the player.
And to an even lesser degree all instruments require the player to pitch them properly, because even with keys and buttons, they still need to be fine tuned while they are played. Many woodwinds get sharp as the scale rises, so the player needs to know to pitch down a little, or certain notes might always play flat, so the player needs to pitch up.
All brass require this, as the base pitch is created by the embouchure, and the player centers the pitch this way.
The keys just give them a greater range of pitches as (I believe) an integral of the pitch they’re currently playing.