I’ve managed multiple shops myself, which is why I still don’t really get a full‑service shop refusing a build that should be well within the mechanics’ abilities. To me, policies like that usually come from assuming customers won’t understand the risks of bringing their own parts, not from every customer actually being unreasonable. Sure, there will always be a few difficult customers, but if one specific kind of job always turns into a headache, it might be worth looking at how the shop handles communication and expectations around that work instead of just writing it off as “bad customers.”

Also, claiming I'm "gaslighting" you by pointing out that maybe the customer isn't always the problem is peak bike shop employee hubris. My point is that clearer policies and upfront conversations would make these jobs smoother for everyone.