The way I understand it (in Kotlin at least) is that if you have a function that calls a lambda function and the lambda function has a "return" keyword, it would be liable to be interpreted as wanting to return also from the CALLING function:

So if I called my_lambda() from my_function() and there was a "return" in my_lambda(), the compiler would interpret it as a "return" from my_function() as well.

In Kotlin, you can allow non-local returns to return from the calling function by using the "inline" keyword or prevent them by using the "crossinline" keyword. Further details here.