I would rather put up with the black screen on my secondary display for a screensaver while the primary display has the optimum resolution for what I need, My comment was more to call out that it appears to be a Resolution conflict that the OS is not able to generate at different levels for different monitors at the same time. It still needs fixing and it does not appear to be hardware related. I certainly would not want to "de tune the res" on mine and we should not have to either.
The software is very clearly able to output the screensaver to multiple monitors at the same time but the resolutions need to match on the vertical pixels output from what I can see and this is certainly a bug that needs to be resolved.
Example:
Primary display 5120x2880
Secondary display 3440x1440
Secondary display will not play the screensaver.
Primary display 2560x1440
Secondary display 3440x1440
Secondary display will play the screensaver.