They may be playing with spec 2, 3 and now 4 to avoid more penalties on the remaining 8 races. Only Max left to have a penalty at Monza, and straight away until the end. Using spec 3 and 4 on races they know will suit them best.
Using spec 2 at Hungary where power is less relevant makes sense, and then using Spec 2 at SPA. Knowing that anyway they wont be able to fight Ferrari and Merc , and not adding miles to the Spec 3 and 4. They tested it with Kvyat, and was pretty impressive. All what they wanted to know. What also is impressive, is that Spec 2 have done now a lot of races. And was good enough to fight with Ferrari and Merc powered cars at Spa