Ive worked in electronics sales. There are sometimes higher commissions for certain brands, and there are regularly special promotions a company may offer in partnership with your retailer to offer you higher commission for a particular brand. For example for a week or two you may get 4% commission instead of 3% for selling that particular brand. Besides sales tactics what we learn, we learn nothing in terms of industry insider info and technical info is nothing more than you'd get off their website or read off a brochure. The store itself may get a bigger cut during that promotion as well. So there are sometimes "off the books" strategies that get passed around on how to steer people to those tvs.
Sony may offer the lowest commission or no commission compared to other brands and the sales people may for that reason may want to steer you to tvs they want to sell. Since consumer reports gives decent reviews for Sony tvs, and unsubstantiated fear about warrantee and service issues will would be really sneaky to fool uninformed customers.