I don't see how all marigolds will not come true from seed? Any ideas?
Just thinking out loud and not having any specific knowledge about breeding marigolds.
In Arkansas I grew marigolds and saved seeds. The original seeds I got were called "French" marigolds and came in various colors and patterns. Most were solid yellow or orange but a few had patterns involving red, if I remember right the word "sparkle" was involved with the pattern. I'd plant them in the garden more as divider markers than for any other benefits. When the garden died down in the fall I'd have huge mounds of bright color.
Photos, people like photos. When I set the plants out I'd already know what the colors were as they were already blooming. I mixed colors in the "mound" just for the contrast. You can see some zinnias in there too. I thought the flowers were pretty.
When I saved the seeds I'd save them by color, even if I had different colors in the same mound. When I planted the seeds I'd plant them in different areas to get transplants. The majority of the plants produced flowers the same color and pattern I planted but there were a few outliers, cross pollination did occur. After a couple of years I didn't even have to save and start seeds, I'd get a lot of volunteers. Some people might consider them invasive.
Marigolds come in different types or styles. Some are tall and rangy, some more compact, some "dwarf". Those characteristics stayed true with mine but I only had the one type. If I were growing different types I'd suspect some cross pollination would go on there too.
I don't know what the word "hybrid" means as far as those named marigolds. If they are crossing growth habits then you would get a mix from the seeds. If they are looking for disease resistance or drought tolerance you'd get a mix from the seeds. If they are crossing colors to get a specific color or pattern you'd get a mix, just like any hybrid.
Here in the US I'd chat with the extension service, especially if I wanted to save the seeds commercially though they'd probably put me in contact with an expert at a university if I just asked. I don't know if your agricultural ministry has something like that. Or you might try contacting whoever is supplying and growing the seeds to see what they have to say. They may give up some trade secrets.
