This never happened before on Android 8.0, and I just confirmed it was not a one-time occurrence by accidentally turning Maximum Power-Saving Mode again. I used Maximum Power-Saving Mode for the first time since updating to Android 9.0 yesterday, and after turning it off, both my Home Screen and Apps Screen were messed up and needed to be reorganized. It appears that the positions of apps that are disabled under Maximum Power-Saving Mode aren't remembered, and after the mode is turned off, are not restored to the Home Screen and aren't rehidden from the Apps Screen if previously set to hidden.
The apps I've hidden still become unhidden on Safe Mode, but my home screen isn't messed up. The only culprit I can think of is Package Disabler Pro for Samsung, which I recently installed to get rid of unwanted Yahoo! bloatware that couldn't be disabled or uninstalled.