devtrackers.gg
Its a rumor that's been spreading around based on the fact that a particular Steam achievement that is relatively easy to get has only been obtained by .5% of Steam players.
All due respect, what you're describing isn't retention.
Retention is a measure of how many players stay with a game over 24/28/36 hours and D3/7/14.
At most, what you're referring to is an overall acquisition rate, per platform, but that's not retention.
We've been saying for quite awhile that we're focused on giving players more reasons to keep playing for longer, and Chapter 1 is only the first step in this. We have more retention focused features currently in development and will be rolling them out in the weeks and months ahead.