This seems like an agitator trying to raise a fuss, not a "whistleblower" (I guess maybe that's how the term is used now). I'd encourage people to read the surrounding tweets, he looks like someone who wants to be outraged about something more than a brave soul calling out some malfeasance. That aside, if this money is for facilitating sessions, as another comment implies, it is perfectly reasonable. The facilitator…
Prof Nelson didn’t call himself “whistleblower “ but it does seem untoward that the main author of the California math framework is also making $5000/hour when the client is not a tech company but a public school district with mostly minority and economically disadvantaged students. In any case, if there is nothing untoward, why threaten him with “police and lawyers”?
That's not "nothing untoward".