Yep, I could see that. And/or, nobody was paying much attention. Just said, "hey, I can get these cheaply and give the customer something that matches the boat."
Ironically, the SeaFit Economy 3-strand pre-spliced are pretty hard to beat for price. $15 for 20-footers. Attwood has 15 footers for $9.35 on Amazon. Might be the same stuff, just re-branded. You can't even get a splice done in your own line for that price--really good deal.
New England Ropes high-strength 3/8" is stronger, but the economy stuff should stretch even better and has a softer feel--not as stiff. Only drawback to the economy stuff is snags more easily and likely doesn't handle chafe as well. I use the N.E.R. high-strength 3/8" for anchor rode (extra strength, don't care about the feel, and it's long enough that you get extra stretch from that).