I doubt that the overlay is helpful for most people who frequent this forum, but it might help new calendar users. I'll ask around.
I do know that I was helping one person get familiar with the calendar, and she was having trouble with a concept that I knew was described well in the help system, so I instructed her to go to the help system. She fumbled around a bit and was unable to locate the help system until I relieved her misery by telling her to click on the Settings icon. That's just one data point, but take it for what it's worth.
Speaking of the overlay, most of the descriptions are links to the help system (for some odd reason, Subscribed Calendars and Settings don't have links; Today doesn't either, but it's quite self-explanatory). When I look at the URLs for the links, they each look something like
https://ue.ldschurch.org/ldsapphelp/cal ... l#cshid=45, but the cshid parameter has a different value for each link. So it appears that the intention is that each link would go to a particular help topic. But it looks like the cshid parameter is ignored, and you are always taken to the main "Calendar Help" page (and I tried this on FF, IE, and Chrome). It would be good to go to the specific relevant page.
Questions that can benefit the larger community should be asked in a public forum, not a private message.