Specifically, edge-drag disregards all the limits placed on corner-drag, allowing you to create arbitrarily large mining tower areas- like, for example, this one:
... Yes, that's the entire map. Shattered Isles.
This strikes me as unintended since it's impossible to get anywhere near this size via the rectangle select tool or the corner drag tool.
Version 4.1 | v0.8.4b (b593)
It would, however, be nice to have some sort of "yes I know there's lag potential" option to disable all the mining tower size limits... probably as a console command. Perhaps separately for global, the current tower, and the current editing operation. Why? I've been known to use very large numbers of mining towers for dumping certain products, instead of just making it a global dump item, because I want dumping to come from a specific surplus storage, everything else to collect at an accept-all storage, and the dumping storage to not empty into the accept-all one, a detail which requires an export route to a tower. Whole-map towers simplify this.