Retina Screen Cross-Compatibility Curiosities

Lately, I’ve been working for a small company doing repairs on a number of corporate issued Macbooks and prepping them for resale. As our stock of new parts started to dwindle, we’ve taken to cannibalizing and harvesting usable parts from some of the other machines with larger issues, and there’s been little issue thus far. However, one of the idiosyncrasies between the Retina Display MBP’s has left me perplexed.

Let’s say that I have two A1502 Retina MBP’s, one is an 11,1 (Mid 2014) model and the other being the 12,1 (Early 2015) model. The screens seem to be identical, at least on first glance, with the connectors on either side appearing to be the same. If I use the screen from the Early 15’ model on a Mid 14’ machine, it works without issue, but doing the reverse (using the 11,1 Mid 14’ screen on the 12,1 Early 15’ model) will give me no display on boot until the operating system loads. Weirdly, the screen seems to function without issues after the unit boots to some form of OS. I’ve tested this with multiple machines and screens and can produce this behavior reliably.

My questions are:

1: Why the heck does this happen?

and

2: Are there any potential issues with using the Mid 14’ screen on the Early 15’ machine? The only downside that I’ve been able to see personally has been that it makes using the boot options menu difficult without having an external monitor or just blind clicking your way to whatever startup device you want to use. The only question that still bugs me is if there’s the potential for any other issues (e.g. not waking from sleep, potential damage to the display port, etc…) since I’m not able to really spend that much time testing them.