Sorry but that mentor has a small practical imagination, a pot can be so large that the top 3 feet that you reach with that spoon could be all oil

True! Consistency and representativeness matter, in soup samples as in social samples!

Is the soup smooth or lumpy? Striated or uniform? For that matter a soup could (and often does) involve huge soup bones that give it important parts of its flavor, but never show up directly in a spoonful. And you might need something different from a spoon to convincingly rule out some specific rare lumpy ingredient.

The didactic value of sampling the soup pot goes well behind its basic function: correcting the beginner’s misperception that a sample’s statistical power is directly related to population size :)

to push this analogy too far, that's because you didn't stir it well, not because the spoon is too small.

Have to sample to see if it’s stirred well enough.

No, you can model whether stirring actions should create a representative sample

Not with immiscible layered stratified flow…

“You're gonna need a bigger spoon!”