All API Group IV synthetics are made from hydrocarbons. However, they can't be crude oil refined hydrocarbons. That's what sets Group IV apart - these are polyalphaolefins built from smaller hydrocarbons.
In fact, natural gas is made into synthetic oil using the Fischer-Tropsch process such that it can not be classified as a Group IV - it is a Group III+.......more saturated than a catalytic-cracked and severely-hydrotreated crude, but not reacted in an additive process. F-T process has interim steps that are very strange, if you look it up. The Germans invented it and used it in WWII to convert coal gas to fuel and lubes.
PAO Group IV is more highly saturated, because it starts with ethane, C2H4, then reacts over a catalyst to increase molecule length until desired viscosity is reached.
Group V synthetics are every thing else - esters, silicones, glycols, etc.