I am just wondering why there is such a long gap between the "GM (candidate)" and the public release and also had those "emergency security updates" in mind, not really a new beta.
And 9.3.3 had been released two (?) days earlier last year although WWDC was later. But who knows... We don't even know yet when the iPhone event is this year what might or might not be the same day of the iOS 11 release.
9.3.4 + 9.3.5 both were security updates without any beta, if I remember correctly. I have to look it up... High chance this might happen again.
But, yes it might simply be they want to make 10.3.3 as perfect as possible for the devices that won't get 11 and might "delay" it until they are 100% sure they don't need another update, maybe they even sit out the risk of an emergency update.
The 10.4 rebranding idea was just because of that very suspicious rumor in mind, together with that long gap mentioned before and those many betas for a x.x.x version (I know it happened before).
We might know more in four hours.