fg gi and reflection in glass

[SgWRX]

in the scene i've been working on lately i came across something. i've duplicated it here... the situation is this:

 

if i use GI only, the glass door is dark.

if i use FG only, the glass door is dark.

if i use GI + FG, the glass door looks like it's reflecting.

 

that's where my question comes in. this is the physical glass mr arch&design template applied to a edit mesh with a shell modifier. i know that for physical glass, it's best to use GI (photons) with it for it to work correctly.

 

my question is, am i seeing a reflection or the fact that light is passing through the glass and illuminating the interior and instead of a reflection it's really a lit interior.

 

now, to add to that question, it's exactly the same material on the large glass windows i have in the scene and they do not change in reflection properties with any of the above situations.