It's not... at least I've never heard such. The 914 made use of some parts sourced from VW GM Tech 2 scanner as it was a joint project with VW. In Europe, the 914 actually said VW-Porsche on the back of the car (the US version was marketed, and labelled, Porsche). The 914's reputation is sometimes lessened by these roots, and it's lower overall performance (although in fairness, the base model was never intended to be anything other than what it is).

The 914/6 however is a different beast. From the beginning, Porsche had planned to market a higher end version that would use all Porsche parts, and this was the 914/6. Factory versions are somewhat GM Tech 2
uncommon these days (although many older 914s have been upgraded with 911 engines to similar or greater spec).

So, any consideration of a 914/6 being a Volkswagon is most likely based on misinformation/ignorance on the part of the person doing the considering.