If you need to change what output you provide by dynamically changing inheritence then I don't see how you can say this alternate technique is OO based.

I'm not into making rigorous definitions of OO, nor am I arguing that this technique is or isn't OO in any kind of purist sense. But considering that it is all about inheritance of methods, I don't know what other drawer to file it under. Remember that Perl's OO is not (much) like any other language's OO. One of the ways in which it's different comes from the highly dynamic nature of the language itself. And this technique is merely an example of that.

If this were available I think I would be pretty safe in saying that I would never make use of it.

It is available. And no, I don't actually expect anyone to make use of it. :-)