When I worked in shops back in the 1970's and 80's any tandem that came in, I hooked the front of the seat over the bike stand clamp. I never clamped the stand to the bike. I was taught that the extra strain and weight on the frame tubes or lugs could cause problems. It's good that the shop wants to make good. It's not good that they didn't know how to work on a tandem safely.
Interesting thing is that even today with my own bikes, I still hook my seat over the clamp even though they aren't tandems. The new thin-walled steel tubes just feel like they can't take any pressure. The only time I clamp my bikes is if I have to adjust the derailleurs or true the wheels. And even then, I clamp around the seat post not the frame. I may be paranoid but I've never, not once ruined or broken a bike under my repair.
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Last edited by drlogik; 04-28-22 at 08:02 PM.