When is search menu glass turns not see-through

I was building something in creative mode and I went to get some glass so I went into my inventory to get some glass. I SEARCHED (does not work if u don't search) g-l-a-s-s and when I grabbed the glass and when i dragged it in my hotbar I noticed the glass above my piece of glass (that im holding) turns not-see-through and looks like concrete.

How To Reprodce:

1) go into your inventory and search G-L-A-S-S

2) drag it down just above your hotbar

3) Look at your glass (that looks like concrete) and scratch your head.

EDIT: Ok yeah I was experimenting with the glitch and I noticed that that the enchanted elytra in my inventory turned black so I got an enchanted book to enchant and experiment with other things but the books turned black too! so I guess enchanted things are effected too. (my resource pack also changes enchantment glitch?)

EDIT 2: a lot of edits, yeah sorry. Ok anyways I turned of my resource pack and guess what...#

it still worked?

?!?