As a consumer myself, it is difficult to always see a contractors work. Customers are not always willing to let you into their home to see what the contractor did.
I think the fabricator may have had good intentions but when the seam went bad they just left it because the cost associated with fixing it was just too high. Probably hoping the customer wouldn’t say anything, all would be fine.
What would really change things if the customer would post the fabricators name and address. That way the next customer doing a Google search may see this thread and steer clear. That is sometime a lot to ask of a consumer because they just don’t want to get tangled in a legal mess with the contractor.