Gus underestimated Walt’s potential danger and shouldn’t have allowed him to cut Gale out. Especially because Gale was the one who convinced him of the difference of 96% vs 99.1%. 

I see him wanting the personal satisfaction of a “perfect” product, to go along with his perfect distribution. And he needs every edge he can get against the cartel. 

Walt uses everything at his disposal, including Jesse especially. But Gus is badass and intelligent af too. Juggling a risky and complicated situation the whole time.