Common misconception, Grumman’s “thoughts” aren’t actually his. It’s just what Major Miles thinks Grumman is thinking. Grumman is known for being extremely strategic and is also certainly ambitious. Despite that he’d never throw Mustang under the bus. Grumman likes Mustang. Mustang is his protégé. And most importantly Mustang has Hawkeye’s loyalty and Grumman wouldn’t risk hurting her, because, fun fact, Hawkeye is Grumman’s granddaughter.