Yep. The tiny space trade-off. A lot of us, having a choice, are going to go for the bigger keyboard so we're not always hitting the wrong keys and making a mess - I'm speaking for myself there, so you can blame ham-handed people like me, OP. When I'm away from home and might have to call or text on the fly, I turn off the auto-rotate anyway so my phone can't swing out of portrait mode just because I grabbed it the wrong way.
That Minuum looks cool, and I wouldn't dare try it; well, I might try it on my tablet, where I've more room to practise. I got the SwiftKey instead, that gives me more language support than my stock keyboard will. I was getting tired of putting my accents beside my letters instead of on them where they belong, even in Welsh, which at least uses the same alphabet. I had to write 'water' like this: d^wr instead of this: dŵr. It's a little thing, but so is a bit of sand in your clothes rubbing against your skin.