Why is this an issue?

Having all branches of a match or if chain with the same implementation indicates a problem.

In the following code:

if (b == 0) { // Noncompliant
  doSomething
} else {
  doSomething
}

i match { // Noncompliant
  case 1 => doSomething
  case 2 => doSomething
  case 3 => doSomething
  case _ => doSomething
}

Either there is a copy-paste error that needs fixing or an unnecessary match or if chain that needs removing.

Exceptions

This rule does not apply to if chains without else, nor to match without a case _ alternative.

if (b == 0) {
  doSomething
} else if (b == 1) {
  doSomething
}