3 payments of 3333.33 for a product worth 10K (with or without the EMI), without ANY other additional charge means an interest free EMI. There is no myth here.
its a trap ,by giving free emi, they are luring the customers to get a taste of their service so that after some time they would come back in the time of need and will buy something and pay interest at a later stage.
just like in british raj , they 1st gave tea free of cost by stopping the commuters , and when the ppl got addicted to it , they started charging (selling) for a price.
some ppl have habit of having tea upto 10 times a day because its addictive, same with emi, ppl get easy credit so they think they must buy the stuff and live a luxurious life now, will pay later in emi's.
also as you said because of emi's ppl buy stuff they otherwise couldn't think of buying on down payment , its a win -win situation for manufacturer also,
all of this leads to the dangerous habit of over spending without knowing easily , spending more than you can afford , its a 'myth' in that sense. makes you vulnerable incase any unknown sudden emergency situation in life.