I know very little of Perl6 and its current interpretation. At least this random source taken from a Google search claims that loop { ... } is an infinite loop, equivalent to the Perl5 construct while (1) { ... }.

You seem to be arguing that the empty infinite loop loop { ... } should be invalid.

Please note that there are external events, like signals or alarms, that can still change the program state in a way that it can leave that infinite loop, or at least, do something else until returning to that infinite loop. The infinite loop is still not energy-friendly, but making Perl6 also force people to behave energy-friendly strikes me as quite out of scope.

But maybe I'm missing the point - I don't get where execution time comes into play at all here. To me, the program execution never continues after the loop statement, and I don't mind whether the loop itself does something meaningful or not. If I wanted something else to happen, I would write something other than loop {}.