I think the chain wear thing sounds like they tried the fixed side, found it didn't work and either actually think chain wear is the issue or just don't have a 3/32 cog in, so attempt to upsell a chain: bingo it would work with 1/8 chain. Basically, buy a 1/8 chain, but ask for the fancy one for the price of the cheap one and get them to fit it properly i.e. not with the quicklink, since their incompetence/fibbing has wasted your time.
I think the chain wear thing sounds like they tried the fixed side, found it didn't work and either actually think chain wear is the issue or just don't have a 3/32 cog in, so attempt to upsell a chain: bingo it would work with 1/8 chain. Basically, buy a 1/8 chain, but ask for the fancy one for the price of the cheap one and get them to fit it properly i.e. not with the quicklink, since their incompetence/fibbing has wasted your time.