Taken straight from Massdrop:
"Scratch-Resistant PBT That Won't Stick
We heard your complaints about the stickiness of Tai-Hao’s doubleshot PBT keycaps, so we took your feedback and acted on it. Now, we’re happy to introduce the same doubleshot PBT keycaps, this time in new colors with a considerably thinner layer of scratch-resistant coating. It still kills 99.9 percent of germs, and the keys still don the two-tone design you love—but this version retains the slightly gritty feel of the original PBT plastic. Compatible with Cherry MX switches, they're sculpted in OEM profile just like before."
Guess what: they "acted" by making it even more difficult to remove the coating with alcohol. I'm warning you because I tried it on one of their PBT keycap sets I bought recently and it's nearly impossible to remove the thinner coating. What's left after treatment is that all the keys will have white blotches all over them and no amount of scrubbing will get it off.
Best bet: stay away from any keycap sets that have this horrible coating.