About organic chemical naming

even assuming that molecule exists, it should be "prop-1-ene".

it should be talking about the same thing, yet it's not common to say prop-1-ene. using the word "propene" won't cause any confusion or ambiguity, as there's only one "isomer" for propene.

As CH3CH=CH2 is a simple molecule and no ambiguity for the propene. The systematic name is propene.

Strictly speaking, the name "prop-1-ene" is incorrect.