Could just be a marketing ploy, to take the embarresment out of buying 'Tiny guy condoms, for the under-endowed' from the shop.
You could be right. The Lifestyles Condoms survey has made me aware that 'standard' condoms are probably too loose for maybe 1/5 or 1/4 of all adult men. So the majority of young teenagers probably need small condoms.
I was a smallish skinny kid and hit puberty a bit late, so I didn't grow into standard sized condoms until I was about 16-17. I first had sex when I was 15. I was worried that the condom would slip off. If they had been available in different sizes back then (late 1960s) I'd have been more secure with a smaller size, but a condom that labels you 'small' might have put me off.
So unless they are packaged in such a way that they don't scream 'this guy has a really small cock!' I doubt they'll sell very well.
When I was in my teens I couldn't bring myself to go into a shop to buy condoms. I used to cycle miles to a pub that had a condom vending machine in a 'gents' toilet (men's room) which was accessible from the car park. I hope there are more options discrete for young teenagers these days.