Edit : The one on the right also probably is using the Deus Ex trick using a second scene/model behind the "mirror", and is thusly not a "real" reflection.
@brokenshakles It would take so very little to add a reflection probe to the mirror prefab to make the mirror reflect the room, at the very least.
Then for the player:
Add a stencil shader to that, to show a mesh only when viewed through the mirror surface.
Finally, a trigger collider checks the players approach, and creates a static mesh instance from the player's skinned mesh (this is built-in to most engines, such as Unity and Unreal, and is used to create trails, pic attached).
I'm not saying it's trivial, by any means.
But when the game costs upwards of $200M, it needs to look a bit better than that.
@brokenshakles The shader isn't showing when the player isn't in the collider.
The collider itself isn't present when the mirror isn't close enough to display LOD 0.
No AAA company does optimizations during development these days, it's always post-release, since they use their player base as QA.
