If you don't trust the shop, you shouldn't let them do the build. You can probably get someone here to say one thing or another, but they have the details, and have met you. That should do it.
While 180 is a totally normal weight, it is upper end for competition tubing. There really isn't any upside to shaving tenths of a cm on a touring bike tubing wall. I don't even prefer a butted tube myself, but that certainly puts me in the outhouse as far as the majority is concerned. For every 1/10 of an mm of wall on a 24 inch tube you are saving 1/2 ounce ish.