That used to work, but there aren’t many proprietary relationships anymore, and even fewer as time goes on.
The people you deliberately aren’t introducing? They’re going to meet anyway.
I expect many managers and talent agents (among others) will learn this the hard way over time.
As information asymmetry decreases, partnerships reshuffle to wherever the value is.
How many connections could be unlocked if people didn’t make themselves middlemen in a zero-sum fashion (or weren't too shy or humble or risk-averse to otherwise introduce)?