These two contradict each other. I would think 20% sounds correct? Never heard of any MFG just changing the color without blocking some level of UV light.
I'd like to tint the front roll up windows to match. Even though it's illegal in CA. I've gotten fix-it tickets in the past, but that was probably 30 years ago.
I do stand corrected in that UVB rays cannot penetrate glass at all, so it does protect against that because it's glass. I'll also amend my statement about IR - since it is darker it will attenuate some heat (IR) to the cab.
The rear windows are ~20%. It is "privacy glass" and is just pigmented glass so won't do much more than stated above.
I have had fix-it tickets in the past (also 30 years ago) for my Toyota Pickup that I bought in Florida with 10% on all side windows. That did not go over well in CA in 1995.
Nowadays everybody is running around with super dark tint on all the windows; so much so you can't see inside of a lot cars during the day...even through the windshield.
My '19 was one of the poor A/C performance trucks so went the tint route to help with the heat: 70% on the windshield, 50% on the front doors, and 70% on all the rear ones (to block out as many rays as I could). Made a big difference and never got a second look from Johnny Law.
Yes it's against the CA vehicle code (specifically only the top 4" of the windshield can be tinted and the front doors cannot be any darker than 70%) but I'm not too far off, especially compared to most on the road and it did not impair my vision at night.