Old docs followed this canvas:

1. There could be many spiders in big projects, some of them can be leaking.
2. We provide useful tools to debug leaks, "which quite often consist in an answer to the question: which spider is leaking?"

I think (1) was justified by (2). But since (2) was changed to just "we provide useful tools" (1) is no longer justified here even if it is technically correct. 

It reads a bit funny if we leave it :) Chapter is called "Common causes of memory leaks", and we list these causes in this chapter:

a) putting objects somewhere to Request;
b) bad developers ("different people");
c) improper resources handling in extensions, pipelines, middlewares.