emergence of very Low thc high CBD legendary strains,what they actually are and where to get seeds?

Hi everyone, Im from EU and I saw this sudden flow of high cbd , very low thc strains called og kush, bubba and similarly named strains after legendary strains. My question is, was this accomplished with these legendary strains crossed with hemp and backcrossed untill they got stable genetics which resembled these legendary lines? It sounds really complicated to accomplish but maybe its indeed how it is been done. Or is it just plain low thc hemp which have been just named after these legendary genetics? The buds I saw on the site looks quite impressive and really frosted. Industrial hemp from what I experienced was fully seeded and not suitable for use for smoking/vaping.
Im wondering how these guys accomplished it and where it comes from, if it is possible to get cuttings or seeds of these plants.
I would appreciate your help guys.