IMHO you'll be fine, but make sure they are brazed with bronze rod. I suspect the framebuilder is just saying "Don't come back to me with your broken eyelet after you let your GF ride on the back rack."

Are these lower eyelets or upper? For the back or front? If you don't want to ruin the paint, for most uses regular P-clips are plenty strong. I don't think you need anything as special as the Tubus ones, but those probably are good. The Nitto P clips are very nice too, in a more conventional way.

FWIW I've never seen a broken off eyelet, and I think I've seen most of the common steel frame failures. (they really are few and far between, but that's a different subject.)