Sure it's possible. I'd be surprised if they didn't being that they've obtain OE certs on some of their oils and those certs require some Gr3 (I'm assuming all GTL is Gr 3 or 3+, but there may be Gr2 GTL. I have no idea).
This. What they do offer is similar performance in terms of oxidation resistance (but PAO is a bit better) and they have similar levels of solvency, IE, next to zero. But GTL doesn't have the seal shrink tendency that PAO has. PAO has significantly better cold temperature performance.
Basically, GTL is just better Group III. Has less wax than traditional group III, so it has better pour points, higher purity and reduced volatility. Volatility rivals PAO and in some instances exceeds it.