Where I'm from, there's a term for adjustables - but it's probably not the place to be using it! Especially as I've just joined! Well done for it working though. I use the top tube of an old bike frame - slots over the ring end of my 15mm but wont quite go over the open end so its ideal!
I think I know what you're talking about on adjustables, but at the same time, while building a tool-kit on a budget, they have their place. Once you have requirement to switch pedals a bit more, getting a decent pedal spanner becomes sensible. Adjustables are definitely not ideal, but have a place as long as you understand the risks, use carefully.
I've eventually got myself small, half-decent pedal spanner, although, it's quite small shaft, but fine for switching pedals on bikes I have.
I like the idea of recycled top-tube as additional lever... just wondered what happened to the poor donor of that top tube.
Big "If" I was getting T-line, I'd be getting them to switch the pedals to some of those new Favero SPD pedals before I rode it away, anyway.