Dunno where you're getting grey $20 denomination chips as a 'standard' color...
At this remove of years, neither do I. My general recollection is that I asked my players, they said "gray" and I checked online and found some support for that but I don't recall what it was. Possibly things like (checking quickly now):
https://www.quora.com/What-denomination-is-each-color-chip-in-poker
But I don't know -- it was over ten years ago now. And...I then found supplies of gray chips, thus completing the circle. Meanwhile gray makes a relatively nice colour for 20s, easily distinguishable from the other standard colours, unlikely to be confused by edgespots and (generally) of a relatively consistent level of visual dullness given the typical white/red/black/purple for the other main denominations (1/5/(20)/100/500).
...as most $20 chips are either black (California) or yellow (pretty much everywhere else).
Is that "
pretty much everywhere else" US-centric? The players that advocated gray here had (mostly) recently moved from the EU (Switzerland, Germany, etc).
I think your tests are flawed. For starters, there is a huge difference between chips with inlays, and chips with adhesive labels. And done properly, neither type should have any effect on the slipperiness of the final product whatsover, since there should be no contact between the inlays/labels of adjacent chips (being recessed), only contact between the chip materials.
No disagreement as to what should be, but disagreement on what I'm finding in practice. For instance Apache Majestics as stickered direct from Apache are significantly more slippery than unlabeled Apache Majestics. Same for Milanos and PGIs (thought from different sources of course). Same again for ASM CSQs with inlays as versus blanks with no inlays. Same yet again for ASM Key West with inlays versus no-inlay blanks. Same again for A and H molds. Also FWLIW for what look like hot-stamped top-hat-and-cane Paulsons versus inlaid Paulsons on the same mold (but I have no idea what chips they are in practice). Etc. In every case using a simple test of a board, a chip stuck down with double-sided tape, a stack of chips atop and then tilting the board, the sticker or inlay chips slide first almost every time, and not by a small margin.
On the other hand, if you are merely slapping on stickers to otherwise flat chips...
I'm the one that wants no stickers and no denominations, remember? I'm not about to go sticker things.
Mostly I'm pretty unsatisfied with what I'm currently finding on market for poker chips. PGIs were are pretty good in terms of high friction (but I'd really like something much more hockey-puck-rubbery-sticky/high-friction), not polishing when left in the car boot for several years (Milanos), not brittle (ceramics, ASMs), a reasonable weight (all the ABS metal slug crap), not (so) thermally sensitive (some ASMs left leaning in a hot car almost curled), and not as generally prone to wear as Paulsons seem to be (that buttery/chalky feel that people seem to like so much is something I specifically want to avoid -- too slippery). Something between a rubbery hock-puck and dry unglazed stoneware...sounds pretty good.
But your blanket claim that adding inlays (or even labels) to chips makes them slippery is patently false.
I guess I'll have to do another video.