Thanks guys,
I will never trust that shop owner again. A reputable guy too, in the vintage/exotic restoration business in the Northwest. Sold me a car recently, I bought it sight unseen, with plenty of emailed photos, but I was also relying heavily on his reputation.

The car failed its state inspection, and the compression fitting was one of several fails - the mechanic explained the same thing about pressure capacity. I think he said compression fittings are rated to 850psi, but brake systems are upwards of 2500. Thank you for letting me just double check whether anyone else used them as a common fix.

The other Fails were due to lack of cotter pins at all steering linkage castle nuts, and worn out tie-rod ends.
None of these issues are difficult or complicated, but that just amplifies the guy's sloppy work and poor service mindedness.

Live and learn,
- Art