The only thing I fault Briere on here is not knowing that limitation, as the CBA language is explicit. Having to wait until now would have happened regardless.
It's also possible that the teams approached the League to ask if the requirement could be waived as a precursor to the trade, as there's really no functional difference between it happening pre-draft or now. Carolina's past last year's cap, they don't have to be compliant for the league year that his contract would have been "illegally acquired" for. We know this happened. We just don't know exactly who initiated it, if it was the teams or the league saying the trade was illegal. If the teams asked first, there's really no fault to hand Briere as the request was sensible, if unlikely to be granted.
And I'm guessing the leaks are from Jones.