I believe you are correct, the Ford GT engine does not have VVT.
But, a DOHC motor can benefit more from VVT than a SOHC engine. With a SOHC engine, the exhaust and intake valves have to vary timing together since they are both actuated from the same cam. With a DOHC engine you can vary only the intake timing or you can vary both the intake and exhaust timing and change the timing on intake and exhaust independently, thus also varying valve overlap. This is what BMW's Dual Vanos system does and parth of the reason why BMW is able to get >100 hp / Liter and >80 lb. ft / liter from a normally aspirated engine.