Update for those with a similar problem. After working with Polycom support, they confirmed there is an issue with the physical mount and the IP550 phones (not sure if the issue extends to other phone models) and the paper template is incorrect and needs updating.
They have opened a service request for this. I will post back here with the resolution.
Update on this.
Polycom identified the problem as a bad plastic mold for the backplate of the IP550 and IP650 phones. Older phones don't have the problem, but newer ones do. Polycom fixed the plastic molds and new phones will not have this problem. Unfortunately if you have one of the many affected phones, the solution isn't simply geting a new wall mount that works with these phones, instead you have to contact Polycom to swap out the phone with an updated back plastic.
Here is a non-inclusive list of date codes that work or don't work with the wall mount:
2008 IP 550 Rev C – Fits wall mount
2008 IP 650 Rev F – Fits wall mount
2010 IP 650 Rev M – Fits wall mount
2012 IP 550 Rev AC – Doesn't fit wall mount
2012 IP 650 Rev Y – Doesn't fit wall mount
2014 IP 550 Rev AE1 – Doesn't fit wall mount
Hopefully there will be an updated SKU in the future to order phones with the correct backplate to take out the guesswork.