On CE 18 I have applied your configuration and even though the module parameter is set as off, docker still reports native overlay diff as false.
It mentions the kernel config parameter in the log warning, wonder if it even checks the actual system.
I've had the issue where redirect_dir=off didn't solve the issue as well. Turns out more recent kernels (>= 4.20) enable redirect_dir when metacopy is on. You need to set metacopy=off redirect_dir=off as module parameters.
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.