From the right vent, if you peer through it you can see the normal entry through the vents. Probably just added detail, the whole thing.

The main oddity is how far it goes down. There seems no point to adding this, especially this far down, since no one is able to see this normally.

But then again, I see no possible beta thing they would be doing here. A huge drop in the vents is highly unlikely.

The beta version used different doors. The grey one had a blue strip through it, and the bathroom doors had the look of the archives doors.

Also note, how the beta guards were the tan ones. There's no huge advantage to switching to green, but they do fit a bit better in the decor. The guards are virtual color changes anyways.

It is possible that Trevelyan walked from the beginning to the end, as in Caverns.

More tan guards here as well.

Another female guard, just showcasing what could've been at one point.

They surely had to have been tested, and their labcoats mostly match.