I concede the point, but counter with the fact that completely flat gravitational fields are implausible, so you could technically distinguish between linear ac

I concede the point, but counter with the fact that completely flat gravitational fields are implausible, so you could technically distinguish between linear acceleration (which has the same acceleration everywhere) and acceleration due to gravity (which doesn't, and hence generates a tide). The effect on a stationary point sized object is equivalent in all three cases. When your object moves then the spinning artificial gravity can be distinguished. When your object is no longer point sized then both gravity and spinning fake gravity can be distinguished from linear acceleration fake gravity.