Red Sex Links are sold under a lot of different labels, but I don't know of any hatchery that markets Red Sex Links as Production Reds. Your right about RSL breeding. They are produced by crossing a red gene rooster X a silver gene hen and the offspring can be sexed by color from hatching. No hatchery that I know of makes that claim about their Production Reds. Red Sex Links will not breed true, but PR roosters X PR hens will always give reddish chicks (not sex linked) whether they are male or female. Because of this distinction, some experts consider Production Reds to be a true breed as in the following quote from Purely Poultry:
Production Reds are a
true breed derived from
Rhode Island Reds and the
New Hampshire Reds. What this means is if you have a flock of Production Reds, they will be able to sustain themselves. Their fertile hatching eggs will results in more Production Reds. If you are a 4H kid or otherwise looking to show a bird, this is the choice for you.
The
Red Sex Link is a
hybrid, created by crossing a Rhode Island Red male and a
Delaware Female. This means that a pair of Red Sex-Link parents will not result in more Red Sex-Links. You must have Rhode Island Red roosters and Delaware hens and
their fertile hatching eggs will result in Red Sex-Links.
(
https://www.purelypoultry.com/blog/...tween-production-reds-and-sex-linked-hybrids/)