Oh, that's what those brushes are. I saw pictures of those brushes before on Rockler's ads, but didn't click on them to see what they really were.
I guess the brushes need less maintenance as you can wait and peel off the glue skin, but for the new applicator tips, you'd need to soak them in the water after every use.
I recall that someone on the forum has shared his applicator tips (3D-printed, non silicone) before, with holes near the top of the tips, while Rockler's have openings on both the top and sides.
This morning, the website still says In Stock Online, and the several stores I checked show a limited stock status.