Yes, I have a Canon P!! I wouldn't have posted my opinion had I NOT OWNED ONE! My Canon P DOES have parallax corrected framing. Perhaps it uses a moving "transparency" within the viewfinder to accomplish the compensation. BTW, my lovely Vitessa L also has parallax compensation, delivered via perhaps a moving mask which "moves" the entire VF image. Works fine!
Stephen Gandy at Camera Quest speaks highly of the Canon P, AND OF IT'S PARALLAX corrected VF. See this:
https://www.cameraquest.com/canonp.htm I will admit that the viewfinder is not as good as that on my Konica IIIa, which has a projected frame, 1 to 1 VF, parallax corrected, and the frame "contracts" to indicate the slight but real change in angular coverage as the lens is extended during close focussing. The Leica M 3 doesn't have that feature, not do any subsequent Leicas, neither film nor apparently digital.
Perhaps your Canon P is defective? Have you mounted it on a tripod to check whether the compensation is working? It is quite obvious checked on a tripod, which prevents one's hand holding influencing the "view."