On managed servers version 9, XDebug was loaded on all PHP websites. To avoid performance impacts on such websites, we disabled most XDebug features by default. Recently, we discovered some edge cases, where the XDebug development helpers have still been active, even though they were not required. As this may lead to a significant performance penalty in some circumstances, we decided to disable XDebug by default as of now.
Therefore, you have to load the XDebug extension in addition to the manual configuration required today already. The documentation was adjusted accordingly.