I'd say you are right about exchanges as all exchanges wallets would be known or quickly become known as soon as a new one launches. Institutional money probably has to be very specific about what and how they trade if they are regulated and using other people's money.

And I agree with what you are saying that if the bitcoin was resting for 5 years and now is suddenly being moved around to exchanges or single wallet addresses it can only really mean someone is going to be selling a large amount soon.