In a more substantive tone, I personally see little value in 5 alpha versions. If none of them progressed to beta or an RC stage, they don't really provide much utility. Why would I try to ship a product unsuitable for production? I fail to see value in a product promised, but as of press-time, yet to be delivered.
Regardless, we can simply look at other frameworks to compare. Foundation 6 is out and is pretty solid. There are various material-design inspired frameworks, and more barebone grid systems that do everything bootstrap 4 can do with it's grid system. Did I mention many are lighter-weight and also production ready?
Since some people take sense 2 to be the opposite of sense 1, it has been frequently criticized as a misuse. Instead, the use is pure hyperbole intended to gain emphasis, but it often appears in contexts where no additional emphasis is necessary.
Perhaps you could have given examples other than Foundation that met your later assertions. Personally I've used Bootstrap for years (2 and 3), tried Foundation back in 2.x days and it was pants in terms of default behaviour of its classes.
It's always looked worse IMO, and I grew used to Bootstrap's sensible (and modular I should say, w.r.t. your 'lighter' comment) ... Sass source structure and conventions, so never been tempted to try Foundation again.
I've seen a few of these 'light' flexbox-based CSS frameworks spring up, but they've always been inferior to Bootstrap 3's grid (e.g. Bulma, which has no support for multiple breakpoints in the grid out of the box).
They've released 5 alpha versions of v4 and released updates for v3?
Do you understand what "literally" means? It's different than "kinda".