I want to register the same issue maybe here is a good place, and suggest this is not a "resolved" topic... I'm getting the same error, and I am very definitely on a LINUX server...
I'll add hoping it might be helpful that I have wordfence installed on two sites in the same account on the same shared linux server, both add-on domains, settings all the same, and that this is coming up on one of them and not the other... The one it is coming up on is pretty new, still early in development...
Some clarity on what is happening would be helpful....
Regards