Glideslope vs PAPI
PAPI and Localizer Glideslope are not designed to coincide or give the same information. It is rarely possible to compare the visual indication with the Glaidepath when you are established on Glidepath. Even at higher altitudes there are discrepencies. As you descend on the glidepath with the autopilot on you may get a chance to compare the two.
In most cases The PAPI instalation is installed on a Non Precision approach runway for descent information below MDA. In other words it is for a visual approach.
Some airports have PAPI which also coincide with the Precision Runway. This is rare in Canada. You will find PAPI on all Instrument runways in St. John's Itl - CYYT. This is due to moderate to severe turbulence, and windhshear.
The reason they do not comapare is that they are located at a different location. The planned touchdown point is often set up at a different location. They were never intended to be the same.
At lower altitudes the visual (PAPI) and instrument signal (Glidepath) often cross each other.