Connected Sides = X-Ray Mode

I made a new type of glass for my mod. I clicked on the option to enable connected sides, which says that only the internal sides will be invisible. I've encountered two issues so far. First is that any block touching the glass becomes black, not showing its texture when looking through the glass. This occurs when I have transparent parts enabled. When not enabled, instead of a black texture, there's no texture. You can see as far down as your render distance will allow you, letting you get a good view of all the caves. While this is a cool feature for something late game, it isn't what I'm looking for for my glass. Is there something I'm doing wrong, or is this a bug?