>An outlet was not designed to be supplied by a stranded wire

That's what you said, and that's just a factually incorrect statement, which is what I was responding to. It is perfectly safe, fairly common, and UL approved to wire an outlet or switch with stranded wire using the appropriate terminals.

I agree with you that OP's little invention would obviously not be a UL listed device, but again, you said that under no circumstances can stranded wire feed an outlet, which is wrong. Now....despite OP having created something that wouldn't be UL acceptable...it's likely not unsafe as long as they did a good job making the mechanical connections. I myself have a "homemade" extension cord feeding a double duplex outlet box. Made it using a 12awg extension cord and a foursquare Handybox. Is that UL listed? No, but I have beat the ever loving shit out of it on jobsites for a long time and it's fine. Many tradespeople have similar homemade extension cord+boxes and beat the shit out them as well.

My overall point is this is almost certainly not an unsafe device to use, but if I were OP i wouldn't have posted it online to show off, because of the obvious and predictable way in which people would freak out about it.