He's right. Technically buying BTC, because you think price will go up and/or because you think you can use it like a currencie is not investing, it's trading and/or using a way of payment.
Buying some token that have a project behind it that is more that just being a currencie is investing. The question is about ETH, because of all the projects that uses the protocol to create smart contract, buying ETH is a way to invest in them all, or in the smart contract system, not only in the currencie.
On the other side buying STEEM is an investment. There is a project behind the token and you can have a return that is more that the just price going up. That being said please upvote this comment to prove me right 😎😎😎😎😎