So, I'm not going to buy a glasscages tank, I've heard too many complaints about their customer service/craftsmanship, but...
Looking at the pictures, I suspect that the only difference between their rimless and rim(ed?) tanks is the plastic trim. If you look at pictures, or have ever seen a glass cages tank, they don't actually put a rim on it. It's trim, not rim. Meaning, the black plastic stuff doesn't offer any support.
Once the tanks reach a certain since, they start using eurobracing, but until that size it appears that, structurally, all the tanks are "rimless".
Just an observation. Anybody else noticed/suspected this.