Can you elaborate? I know some people were paid big $ up front to make the move, but it didn't seem very secret -- the ones I'm thinking of were pretty open about the deals they'd taken, so presumably Substack wasn't pressuring them to keep quiet. And as far as I know they were paid up front for the first year, before moving to an ordinary revenue split and being free to leave.
What you're describing sounds like a cash advance/guarantee which Hamish mentioned about 'de-risking' offers.
If you have good data that a writer could make X money, but they're afraid to leave their day job - it's easy to just say to them "we'll pay you your day job salary to de-risk this jump for you" if you know they'll make way more than that. You can even offer more.
That's not a 'secret benefit' to prevent them from leaving - it's a smart economic move to help people anxious about perceived risk.
The benefits I'm talking about are not the advances or guarantees, there's basically a ton of secret programmes at Substack where they give favored publishers special in-kind benefits to effectively pay back some of the 10% fee. Hamish knows what I'm talking about, but can't mention it publicly because their business model is reliant on a pretense that every publisher is paying 10% and not a hodgpodge of subsidies and kickbacks. Does that make sense?
It’s also possible to directly discuss this openly/honestly like you did in this reply (thanks for clarification) vs. indirectly via disingenuous hostile snark in your first comment.
Also looks like there might be some sort of conflict of interest based on the work you do in your bio which could be having a possibly unintended influence.