From spec, 3.11.2:

Two call or construct signatures are considered identical when they have the same number of type
parameters with identical type parameter constraints and, after substituting type Any for the type
parameters introduced by the signatures, identical number of parameters with identical kind (required, optional or rest) and types, and identical return types

Nowhere does it say that type parameters should have identical names.

But this code is highlighted with error in playground:

class c {
    get x(): <T>(a: T) => T { return null; }
    set x(p: <U>(a: U) => U) {}
}