That is one theory.
In the 1950's a few Russian scientists began questioning this traditional view and proposed instead that petroleum could form naturally deep inside the Earth. 'Dry' wells have mysteriously refilled. This so-called "abiogenic" petroleum might seep upward through cracks formed by asteroid impacts to form underground pools, according to one hypothesis.
Lots of different opinions.
That oil and gas is only sourced to sedimentary basins is more than just a “theory”.
No. That is a fact.
No commercial oil production anywhere in the world outside of sedimentary basins.
proposed instead that petroleum could form naturally deep inside the Earth
That would be a theory. It doesn't follow many of the realities of where oil is found.