Because the game is a beta there are many bugs. I am sure this is one of them.
Rule #13
Do not exploit bugs or glitches: If you find a bug or a glitch in the game that provides an unfair advantage, let us know about it instead of using the exploit for your own benefit.
Tell me again how going...
If the glass broke and you took damage from jumping through it, then no it wouldnt be exploiting. But since it is 100% quiet, aside from foot steps leadtime up to the jump, and you take no damage from going through a window, it is exploiting.