Spam and scam are two different things, in that case, you should call him a spammer, not a scammer. To promote strongly in Steam new updates when those aren't in the site, it's a fair critic. Although it seems that Steam has no rules against it.
Regarding short updates, the most of the devs here don't make updates with more than 500 renders, the amount that this dev and his team makes, so, I don't know who are the legit devs then. In my opinion, he is very legit and actually is trying to be very professional. To put an example, when many people complained for the recent Julia's update, he made refunds for the people who requested it, nobody else does that. You also need to consider that they are making Forbidden Fantasy too, if you compile both games, the rate of production is way bigger than the most of the games.