I could be wrong, but I think he meant water SOLUABLE flavor. When I was checking out flavors at a local spice and coffee shop, they had both oil- and pg- carriers in the flavors. The oil-base flavors might be fine in cooking recipes, but not vape juices we inhale.I’ve never seen a flavoring that wasn’t pg based. I’ve heard of VG based but never seen one. There are water based ones?
As far as availability, I think the nic will be the block for DIY liquids. The other ingredients for juice are used in other DIY things like food and cosmetics.