Likewise some authors argue that the existence of tidal effects and geodesic deviation conflict with the equivalence principle, but that too is clearly not the case, provided we properly restrict our attention to a sufficiently small region of space and time. Fundamentally, those who argue against the validity or meaningfulness of the equivalence principle are focusing on the wrong level of attributes when they point out that gravity and acceleration are generally distinguishable. In making this distinction they focus on one or more extrinsic attribute, whereas the equivalence principle is really an assertion of intrinsic equivalence. Indeed, it is the perfect intrinsic equivalence that makes a purely geometrical interpretation of gravity possible. There is no additional coupling present to produce the effects of gravity on a test body.
Gravity is geometry.
This is expressed somewhat informally by saying that if we take sufficiently small pieces of curved and flat spacetime we can't tell one from the other, because they are the same stuff.