If I were Chevy, I would be pissed too. Even though Chevy has won the first 4 races, Honda has been very competitive and now is more competitive. And these were all street/road courses, where Chevy should have the advantage, ceteris parabis, with a twin turbo vs. a single turbo.
Chevy did seem to have a slight advantage on the straights at the first few races (1 - 2 mph?), but was at a disadvantage in Brazil after the turbo switch by 1 - 2 mph, so this seemingly has added about 3 mph to Honda's topline speed.
Adjusting for drivers' past oval competency and using a small data set from the test last month at Indy, Chevy had a slight advantage (about 1 mph), and now Honda looks like it will have a 2 mph advantage with their engine/turbo. That is huge at Indy.