I actually agree with Phil: Sony's Reasoning For Blocking Cross-Play Is "Unhealthy,"

[Neodegenerate]

Hiku said:

Neodegenerate said:

The bolded is speculation that if 15 million XB1 players are online playing that game with 3 million PS4 players MS will come out and say that on Live they had 18 million MAU for that timeframe.

Ah. And what does MAU stand for?

Monthly Active Users.  It is what they use in their PR instead of units sold to indicate that they have a healthy ecosystem.