Ah yes, I thought I had pointed out the whole deal with needing a strap for each guitar. I was wrong. That's the way I'm set up anyway, though. I'm very picky about each guitar having its own personality, so they all have different straps for the simplicity of changing guitars and for the individuality of the feel.
As for the torque on the strap button screws, I don't see any reason they would put any more torque on the screws than the plastic twist-on type strap buttons. The washers are free to move around the button.
As for scratches, there is a strap between the washer and the body of the guitar. The washers won't scratch your paint. I, personally, am not worried in the slightest about scratching my strap buttons. They are cheap and serve their purpose, scratched or not, and nobody ever sees the bottoms of your strap buttons. (Especially if your strap is always on the guitar.)
And yes, I concede, if you only have one or two straps that you like, or if you tend to sit down with your guitar and the strap bothers you, this is not the system for you.
Barring that, though, I don't see any of the reasons listed as valid unless someone can explain to me how washers would torque the screws worse than the plastic strap holders, though I do appreciate the concern.
By the way, Mick, muchos kudos for proper use of the word caveat.