Probably because it's hyperbole. I've been using element web for a long time and have not seen those kinds of issues. Not to say that it is perfect, there are definitely bugs.

I am a power user and have never experienced this. Their system must be disk bound or ram bound or something.

Granted I have 0 systems I use with less than 64gb of memory. Ram is cheap.

I don't think that is normal, at least I've never had any client take that long to load, and nobody I communicate with on matrix has ever mentioned that as being an issue either.