Your NBC article describes it as “a gray area of law.” In plain English that means “not illegal.”
Many pols do it. The FEC has investigated others for it but done nothing about it. Why? Because it’s not illegal.
What is occured is
You (as an example) form a pac, and get millions in campaign donations to run a state office.
You now have 10's of millions left over in the pac.
You file paperwork that says you're not supported by the pac anymore, and have no communications with it.
You then say you're running for a federal office.
The pac now magically funds your campaign by giving those millions into a federal pac.
The money is the same money, so it should be illegal. The FEC, being 3 Rep and 3 Dem, deadlocked along party lines on the donalds case, so there is no clear ruling that it is illegal.