Nutaku is not only about adult games content
There is on the site nutaku a tab "games without porn"
The agreement between steam and nutaku has already taken place because as I have said several times "crush crush" and "everlasting summers" were steam games before being on nutaku and are now on both platforms
Removing content is easier than adding
The steam versions of crush crush and everlasting summer are much more soft than that of nutaku
Edit the content of flower knight girl to add a reel multi player is possible, I do not say that it is easy but it can very well be discussed
All the more so that everyone will win
Nutaku has additional advertising and a much wider audience
And dev either they use nutaku or not will earn more money than the game is popular or not