From, what you linked - thanks for that by the way.

DAU measures the "stickiness" of an online product by answering the question, "How many unique product users visit the product daily?"

So it would be closer to

Active user on a day is anyone who does any action registrated via blockchain, including resteem, voting and of course posting.
In future only playing steemmonsters will also be something we see more often by accounts and those have zero comments, posts and votes.

And those are more closely mirrored in the roughly to be said 50k users.

Hmm I am curious now, I'll look for more detailed data on this.

Great, keep it on!