And those responses show why this issue will become more widespread in 2023. For the past few PBPs, there has been evidence of a significant (and increasing?) number of riders arriving at intermediate controls out of time but getting to the finish in time and being homologated. Jo (formerly OTP) created a similar graph last PBP
http://gicentre.org/pbp2015/ but it didn't look nearly as dramatic as this one.
In '99 and '03, some full value friends that had left intermediate controls as they closed mentioned how noticeable it was that riders were pushing hard to get their brevet cards stamped inside time. Apparently, as the intermediate controls closed for the 80hr and 90hr massed start groups, there was an obvious reduction in the number of riders arriving. With the more recent staggered starts, this behaviour wouldn't be obvious, except in the online timing, but it appears that riders are becoming more relaxed about being out of time at intermediate controls.
The original purpose of PBP Randonneur's intermediate control opening and closing times was to approximate the original Audax average pace schedule (now set at 22.5 km/h on the road). That was why early PBP randonneurs had to sign out of each control in addition to signing into controls. When the randoneur average speed limits were explained to new riders, they were told to imagine that one car was travelling along the route at the maximum allowable average speed and another car was doing the same at the minimum average speed. The rider's aim was always to stay between those imaginary cars, regardless of eating, sleeping, mechanicals or anything else. As soon as the second imaginary car passes the rider, the rider is out of the brevet. A similar system applies to riders and the broom wagon at cyclo-sportives and the Tour de France.