The proposal is now in review, so it'd be best to provide feedback in the official review thread @SlugFiller: SE-0462: Task Priority Escalation APIs
I can answer here though: our structured concurrency primitives are not powerful enough yet, e.g. we'd like to share a task group into child tasks and be able to add tasks into it from them -- we don't have a model for this yet where it would not trigger concurrency safety errors, and it'll require much more work in the typesystem and library to support these. We'd also be able to get rid of the with... methods for task groups along this work... but for now we need to support escalation with existing tasks, and this functionality has existed but was internal to Swift, we're making it available to low-level concurrency library authors, which does not preclude continued improvements in the structured concurrency story.