Notably, this does not show up in the editor. I haven't got it to reproduce outside the jquery project either:

• You can see this error with npm test jquery inside Definitely Typed.
• Or you can observe that tsc before Support re-aliasing of type alias instantiations #42284 has 12 (expected) errors, whereas tsc afterward has 14 errors.
• Or you can paste this code into a test file (I used jquery-slim-no-window-module-tests.ts), since it's a smaller repro:

function delegate_0(events: string, handler: JQuery.TypeEventHandler<HTMLElement, any, any, any, string>) {
    delegate(events, handler);
}
declare function delegate<TType extends string>(eventType: TType, handler: JQuery.TypeEventHandler<HTMLElement, any, any, any, TType>): void;

Expected: No error on the argument events

Actual: Error on the argument events: "Argument of type 'string' is not assignable to parameter of type "myEvent"."

It looks like TType is inferred as "myEvent" instead of string. I can't figure out why. TType should be constrained to string | number, since its constraint as written is TType extends keyof TypeToTriggeredEventMap<TDelegateTarget, TData, TCurrentTarget, TTarget> and TypeToTriggeredEventMap has a string index signature (plus a dozen properties or so).

Changing events to "myEvent" gets rid of the error.