I used milk jugs though that might not be the best solution (and I am doing it in pots on some things this year and thinking maybe soda bottles for something I'm planting next week), because I was decimated last year by slugs that got in where I cut the milk jugs. It depends..sometimes you get hundreds of seedlings, sometimes you only HAD five seeds to start with (like some peonies I planted). The goal is usually to get enough that I get seeds to get more (or divide). That's kinda like asking how many kids do you want, and everyone will have a different answer and it's all meaningless to anyone else. And the answer for every species will be different. For me, and for typical things I can expect upwards of 70% germination. Whether a grasshopper lands on the porch and eats them all (happened once) or slugs devour newly sprouted, doesn't come into the picture..that could happen no matter what you do, and has nothing to do with winter sowing techniques/procedures. That is simply the nature of nature. I haven't done anything seemingless ridiculous like winter sowing tomatos. There's no point for what doesn't require cold (at least to me), though I've read that people do such silly things with tropicals and many respond well to it and germinate when temperatures warm enough). Sometimes I suspect they use the same techniques and plant in March or April and call it wintersowing...thus some confusion.

As with your question about currants I'll say again that you'll get far superior crops if you use cuttings or divisions from named cultivars. Growing from seed will probably lead to disappointment and could well be more expensive in the end that just buying a plant. Certainly it will take a lot more of your time.

It's Gigante. This year they are carrying it in the bologica line instead of Franchi. I got my seed in 2019, heh. Seeds of Italy sometimes switches between lines depending on what they can get I think. But their packets are large enough that one usually lasts me a couple years. I'm hopeful that what I'm overwintering now will go nicely into the spring. I got the quarter pound of it from Johnnys because I want to put in a small parsley hedgerow in the new gardens I'm working on for the spring.

The question was why moist stratification doesn't kick off germination. I cannot plant these too early because the plants are needed for bank stabilization in a creek that is prone to flooding. Such flooding would clear away ungerminated and thereby unanchored seeds. So when I plant, I want them to grow, like immediately. MIght have to protect, but that's a big job. I could plant out plants, but those are vastly more expensive. So if the seeds are all downstream, that doesn't achieve the same result as moist stratification.