To me, the layperson, the idea that you cannot distinguish whether you are in an accelerated frame or in a gravitational field seems wrong due to a very simple fact.
The force that would be exerted from acceleration versus gravity is different. The force you we think of as gravity comes from a center point that changes with your position while acceleration comes from a uniform direction without regard to your position.
You're thinking of a specific gravity scenario versus a specific acceleration scenario. But the equivalence is true, it was one of the things shown by Einstein.
The force that would be exerted from acceleration versus gravity is different. The force you we think of as gravity comes from a center point that changes with your position while acceleration comes from a uniform direction without regard to your position.