Both forms of thought are understandable.
I think the list Eric has put together is agreeable for me. Although I understand where A3n is coming from, and he's not wrong in that you **know the map prior to playing**, but only ~half our library of 1300+ has Flying? And then only so many of that ~half have decent Move or Range. So it's a bit of a shame to essentially say "you know the map heavily favors figures with Flying, and even more so the ones with above average Move or exceptional Range, so I better limit my options to them if I want to stand a chance or have an equal shot to win..." Same mindset with lava maps and tossers, to an even more hyper focused/limited group of units that gain a big advantage.
So while I don't fault you or anyone else that may feel that way, but IMO, that's the distinction between competitive and casual that should be made. Casual = no focus on equal odds for the overwhelming majority(at least 80%) of our library. Competitive = as equal of odds as possible for the majority of our library.
Ultimately, I don't see any harm in more strictly distinguishing something as Casual vs. Competitive, as it shouldn't dictate any sort of map quality or fun factor etc. Nobody should feel discouraged for making a Casual map as if it's somehow inferior. If anything, it's a label to help newer players play on something more guaranteed to not heavily skew/favor one team over the other if that's a concern at all.
All that said, a tourney held specifically on Casual maps would be fun. But understandably, that sort of then requires you to build around those maps rather than what you may want to play. If you're in the mood to run Criminals for example, you better think twice.
**In tournaments, you may know the map pool, but you're stuck with a pre-chosen locked in army or limited draft roster.
**With playtesting, just because you know the map, doesn't mean that unit should be played on it if its going to heavily skew the results, something newer players may not fully grasp.