ive had the opposite actually, Id sold tiles and adhesive to a customer in our shop. They were 45 x 75 Grade 5 porcelain on walls. So i gave them Rapidset and AD1, and theyre tiler told them i was ripping them off and that it wasn't suitable at all, and if he used that then they wouldn't stick, he said they only needed green star. They came in mouthing off to me about me being a crook. Took me bloody ages to explain to them that i was exactly right and theyre tiler had no clue what he was on about. Ended up proving it by asking the customer to use our phone and phone bals advice line... and bal told them to use rapid and AD1. Result!!!
Just wished hed have phoned me and queried it before mouthing off, cos then he wouldn;t have looked stupid and lost the job.
Dunno if most companies do this, but most our sales staff are qualified tilers, and theyve all been on various training courses for adhesives etc before theyre let loose on the shop floor.