Look at their wallet, it seems they have already sent 13500x5+1724 = 69224 ether to exchanges.
Please note that the $50m presale from the hedge funds (Blockchain Capital, Pantera Capital, and Polychain Capital) is very likely received in fiat (Please correct me if I am wrong). There is no strong reason to sell that much ether into fiat so early like that.
I think it means they do not believe in Ethereum, and they have no interest to help making the whole crypto ecosystem stronger and more valuable. What they care is their fiat. If they believe in crypto is the future, why selling so fast? why ignoring all the crypto investors here?
These are indeed red flags.