I read it as a fairly mathematical statement of fact. There is a tree of opportunities, and one can choose to prune some of them at the root. By definition, any direct/anticipated; and any unanticipated, indirect opportunities; are gone. Which is a 100% valid personal choice, I interpreted the minor quibble being whether this is a net positive creditor to their overall success. On one hand, pruning opportunities is in principle a negative; on the other hand, time saved not dealing with undesired channels is a positive.
The reluctance to work with recruiters is mostly the "time suck" element. If you were to chase every opportunity sent by recruiters you'd waste a ton of time, but you'd also maximize your potential for getting offers that meet your criteria (whatever those criteria are).
It was meant as a statement of fact. To oversimplify, if you limit the information you are willing to receive, you won't have all the information you could have.
My main issue with the original post was that OP was crediting a policy of reduced information with doubling their salary. That just isn't the case.
