That is all true. Stations that air AT40 (current Ryan shows and classic Casey shows) are giving up five minutes an hour and assuming they don't oversell the show that can be significant. I just can't imagine the 11am hour on a Sunday is that "make or break"
When we aired AT20 and Backtrax 9-10 years ago, we never were able to get more for ads that ran during those shows. I honestly don't even know if stations try to upsell shows anymore, my guess would be no. Which is why running AT40 from 6a-10a is so desirable. It is easy to lose five minutes of the 6am hour on a Saturday or Sunday to national ads. Folks start to tune in around 9a - just in time for the last hour.
Not just nowadays, but when has Sunday at 11am ever been "make or break" for a station? AT40 has been running in that hour on many stations whether the show has been popular or not since the 70s
Remember - in the 70s stations didn't have to give up any local commercial time to air the show. And even into the 80s when they did, radio was a whole different ballgame and they could charge high rates for advertisers during a popular program like AT40.
These days you really can't "upsell" a show like AT40 to advertisers. And to a major market station - giving up five minutes of local spots in a late morning hour on a weekend is actually a pretty big deal. Weekend middays are actually a pretty highly rated daypart in many markets, which is why many PDs want AT40 over by 10. This way they can get their local content on and have the hour to themselves both programming and ad wise. Which is why you have so many stations that air the show from 6am-10am. It's not that they don't want people listening to the show. But they would actually wind up losing money by airing it in a higher rated daypart.
In some places I can't imagine 11 could be that big a deal. Orlando? I can. That d**n Disney Springs is packed by 11 whenever I've been over there. People are also starting to get out of church. Not to mention the other theme park traffic. I'm surprised New York and LA run the show from 8-12 Sunday's honestly. I know KIIS does Saturday too but that airing doesn't include the network commercials. You would think they'd do it the other way around.