I posted about Kleins I'm currently using but I'm not defending them, was just sharing my experience. I'm not really a big fan of Klein anyway but I have a few things from them. I just got the ones I posted simply cause they glow in the dark, not cause they are Klein.
I work mainly in automotive so I don't deal with solid wire much, just the occasional home DIY stuff. Stranded wire is what I deal with the most. I wasn't saying these types of wire stripper/cutters shouldn't be used with solid wire, I just don't cut solid often.
The wire strippers are designed to strip solid wire also so why not cut solid wire? In his video that's the only other thing he's cutting so I'm assuming it's the solid wire that is causing the damage. I don't remember all the details in the video but did it show how long/many cuts until the damage occurs? I know he likes to do excessively long cut tests with knives.
If it is the solid wire causing the damage then that's a design flaw or as he reports insufficient heat treating. Seems like these are one of those tools where someone copied someone & now everyone makes them the same regardless of their flaws or whatever.