Did ST intentionally remove this mobile breakdown where the two columns turn into one column at lower resolutions? Because that's how it used to be. Or, is this a bug and the mobile breakdown isn't working correctly? I need to know.

Hi, Pantheon

I've forwarded this thread to the developers. Once I know which direction they're going with it, or what the explanation is for the change, I'll post here. 

Just to follow up on this, the devs took a look and modified the media queries for various pages to make them more presentable and functional. Previously, we used some modified flex styling, but obviously improvements were necessary. Look for the changes in our next public release. Thanks for pointing it out, Pantheon.