TYPO3 Core

\TYPO3\CMS\Extbase\Persistence\Generic\Storage\Typo3DbBackend fetches the PageTS via BackendUtility::getPagesTSconfig($storagePage); in line 719.

This is a bug because that method already returns cached data and the cache algorithm inside that method is even better than the one Extbase comes up with.
If different pages have the same PageTS, it will only be cached once. As soon as Extbase kicks in, it fetches the PageTS from the BackendUtility and stores a copy of it in a static property. On top, Extbase always copies the PageTS, even if the PageTS for different pages is the same.

In this case, the cache can simply be removed at all.