I have bought wines at vineyards all over France and live in the middle of a wine-growing region, but I've yet to hear a vigneron speak of dégustation horizontale. To quote the infant Ash from The Crow Road, it sounds like a load of bollocks. And affected bollocks at that.
I strongly suspect you are right. My vast knowledge of wine trivia has been acquired from my brother-in-law, he is a collector. He often feeds me copious quantities of wine and as he pours he talks about bouquet, clarity, vintage, and vintners and all I think is, "keep it coming" In the end, when it comes to wine all I know is, if I like the particular wine or not, not to drink to much, and a bunch of useless trivia and I think that is were the bollocks part is.
The most profound piece of wine lore I ever heard was that there were no great wine, great terroirs or great vintages; there are only great bottles. Originally said in French, where grand means large more often than great does.