I haven't read much on internal brazing. I have a C. 1983 Peugeot P-4 Corbier, which I think for their later models fits me and rides better than the UO-8. (Then again we all have our preferences)

The bike was a base model.

It's HLE tubing, which is probably in the same grade as Motobecane's 2040, a slightly higher grade of Pipe-de-gas.

I suspect the bike may have been soft-crashed, as the fork is slightly off (bike tracks slightly to the right) but then again that could just be a bad fork bending at the factory. The bike doesn't have rippled paint or any other telltale signs. Generally, it rides quite well.

The frame joints look fine.

The "Internal brazing" looks impressive, I'm just wondering what's your experience.