I'm not sure I agree. To quote one of the cases:

>For example, at some point, Debian updated the fontconfig package by backporting an upstream fix for a memory leak. Unfortunately, the fix contained a bug that would crash Firefox and possibly other software too. We spotted the new crash only six days after the change landed in Debian sources and only a couple of weeks afterwards the issue had been fixed both upstream and in Debian. We sent reports and fixes to other projects too including Mesa, GTK, glib, PCSC, SQLite and more.

That sounds a lot like Linus' "many eyes make all bugs shallow" idea working as intended.