Robin Lauryssen-Mitchell send me an email noting that he could not replicate point 1 under 14.2 beta — I updated my MacBook Pro 2018 to 14.2 beta and the screen dumps (with CTL-CMD-3 which also works OK) are exact replicas of the screen, size and color are both correct. So it appears that Apple fixed the problem for an upcoming release.
Thanks to everyone who helped with this issue.