He should have. Yeah I mean we can all agree it would be nice if he spontaneously developed the skill set you’re describing. But we’ve literally never seen him offensively grapple besides clinching for shoulder strikes. It’s always a means to get back at a distance.
His losses have always come via submission besides poirer, and he only ever had one sub which was an RNC in cage warriors. He’s not looking for subs, either because of his gas tank, or he lacks the technique and skill to do so. Either way, saying he should engage in the ground with poirer is a bit silly considering poirer has submitted some very talented sub/bjj guys like pettis