But the columns are Ionic, it uses a post and lintel method, the entablature is not Etruscan and the front room could well be a cella.

At the same time it is true that the peristyle colonnade is not there, which matches some Etruscan styled temples (just columns on front), though both the Temple of Athena and the Erechtheion don't have a peristyle colonnade.

For what steps are regarded, some temples only had crepidoma across the front façade, like the Lycosura temple, which would both match the frontal colonnade with no perimeter and the frontal crepidoma that doesn't have sterobates around the temple (like is common).

So while unorthodox, I don't see why this would be Etruscan or "Roman".

That's a great observation, after all that temple is a hybrid between Etruscan and Greek. (And the columns indeed are Ionic).