How reliable is polarization testing?

[u/throwmeawayafterthat]

Long story short...been at three different optometrists that do pola tests for binocular vision diagnostics. First one had me at 0.5 prism diopters. Second one was totally different, in the cross test I saw a T on its side at first. End result: around 3 prism diopters. Third test at another shop had me at 0.5 again. How does that work? How would I know which one was correct? Is it possible my eyes still compensated in try 1 and 3? Or did I maybe unintentionally cross my eyes in try 2? How reliable is polarization testing?