Think of events like the 24h Race on the Nürburgring. The track that is used cuts the Mercedes-Arena and uses the Yokohama-S instead. I can't figure out a reason why that is done.
The argument, that it is done, so the area can be used for additional paddock size doesn't seem logical to me, because when the Nordschleife is used with the version of the GP-Circuit, which cuts the entire lower part of the track, the Mercedes-Arena is used again. This seems grossly inconsistent to me.
The argument that the GP-Track is used just so there's a reasonable space for boxing and the Nordschleife is the main event, so you want to "cut to the chase" also seems unreasonable. Wouldn't it be most logical there to cut both the Mercedes-Arena and the entire lower part of the track?