That's a backronym. VHS originally was an abbreviation for "Video Home System".

Edit: also, the helical scan on a VHS tape can't really be said to be "vertical". A helical scan already implies a direction along the length of the helix, and "vertical helix" doesn't really make sense in the context of scanning down the length of a magnetic tape. Adding "vertical" to the actual term "helical scan" can really only be an attempt to back-fit an acronym to "VHS".