He straight up was less smarter, it was stated all the way back in Immortal Hulk #2, although he is still fairly smart but as Vordan said, not a super genius that can make time travel machines from a toaster. But it seems Cates has either ignored that or has reversed it because we can see that Banner can build a mech for Hulk. Either way even if he wasn't super genius like before he isn't a moron and wouldn't just dismiss his computer telling him his gamma levels doubled out of nowhere as "probably nothing".