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That sounds like hot staging, which they've been doing for a while now.

https://en.wikipedia.org/wiki/Multistage_rocket#Hot-staging

I assume that SpaceX doesn't want to completely shut off the Super Heavy engines during separation, in order to avoid the requirement of ullage thrusting for the boost back burn. But hot-staging is really hard on the equipment. It's like having a flame diverter directly below the Starship's raptors. And it is known to have caused problems in previous flights.

Yep. And the hot staging interstage they're currently using as a flame diverter is expended, expensive, and heavy.

So many of the fixes that I've read about add weight, that it's going to be interesting to see what fraction of the originally intended payload capacity remains,

Gen 2 booster will replace the ring with struts.

> to avoid the requirement of ullage thrusting

To expand, this has to do with keeping liquid propellantws settled. If you stop thrusting your propellant will start floating around in zero g. That means you need to thrust to settle it back down before you can fully engage your engines. That complexity is sidestepped by just keeping the engines running at the rocket equivalent of idle.

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