"Though I guess there's nothing to prevent a casino from making all their chips oversize if they choose to"

Casinos have to get a waiver from gaming for oversize chips (41MM and up) that don't say "Bacarat" or "Sports Book" on them.
We have oversized NCV chips 43 & 48MM that were waivered in.

"Palms did, even if only by a silly millimeter"
B&G got permission to produce the 40MM regular rack chips.