In a world where bugs are certain, unpatched (because a bug is known but a patch hasn’t been released) e.g. iOS is nominally not more secure than patched Linux, unless possibly if you are a nationstate actor hoarding zerodays. The speed of patching bugs is important because most targets aren’t big enough to be on the receiving end of a zero day. Though I do agree that this doesn’t really say anything about whether one system is more or less secure than others from a design standpoint, it certainly matters from a practical standpoint.