I wouldn’t touch that stuff.
I doubt many window cleaners do.
Hypo is much much safer (though still dangerous)
My dad worked with neat hypo for years and years (technical manager at Leisure Centers with pools)
He’s had neat hypo in his eyes, skin and hair, to absolutely no ill effect (15% hypo). Washed quickly and thoroughly off it is fairly easily dealt with.
This isn’t an excuse to not be very careful with hypo, but when it’s watered down in a softwash mix, it’s pretty much harmless. If you get it on your skin neat, it needs to be Washed off quick! But you won’t end up with feet like that 😮
This stuff that’s got to this lads feet is a completely different level, and I wouldn’t touch it!