Well, as I believe has been pointed out, people in sports at the moment are extremely wary of messing with concussion injuries.
What we're hearing from Daniel Bryan is that a doctor in Phoenix who worked at an unspecified Super Bowl has cleared him to wrestle. However, I've done quite a few searches and haven't been able to find the name of the doctor he is referring to. So we really don't know much from that viewpoint.
You would think if Daniel was that adamant that he was okay, he would be putting forth more than just one doctor's opinion. It could just be that his doctor isn't as cautious as WWE's doctors are or he could have different criteria for what he considers 100%. The man was a doctor on the Super Bowl, so he knows football, but he may not have as much knowledge about professional wrestling as WWE's doctors do.
Personally, I don't think Daniel Bryan is trying to sneak back in or anything. But it just seems a bit odd to me that he is saying that a single unnamed doctor who he hasn't tied together with any knowledge of professional wrestling would be all WWE's doctors needed to agree to clear him.
Despite the fact that they might not see Daniel Bryan as their head guy or want him as their head guy, I find it hard to believe (especially with the weak Raw episodes of the past months) that they wouldn't want to utilize Bryan as quickly as possible. So, I tend to think WWE is likely doing what they honestly think is best.