Stained glass and other tinted object turn completely transparent while pushed by a piston

What I expected to happen: A (sticky or non-sticky) piston pushes a stained glass block, and stained glass block keeps tint all the way through the push

What actually happens: When stained glass (or other stained objects, including ones added by mods such as Forestry (forestry.sengir.net) and Minefactory Reloaded (http://www.minecraftforum.net/topic/2016680-162164-powercrystals-mods-minefactoryreloaded-powercrystalscore-and-netherores-updated-mfr-275-released/) (these mods were for 1.6.4, but the same thing happens with the chosen versions (tested by adding a block myself)) is pushed by a piston (sticky or normal), then, when in the entity state, the tinted effect is removed.

Can it be reproduced: Yes, on Windows and Linux (haven't confirmed it on OS X)

Proof video (could not attatch): https://www.youtube.com/watch?v=SE26BGUNlLw