Are you saying it is not possible to prevent the time modification on the device files, due to MTP.
If so, will it not be fixed in Android 9?
If Google really wanted, they'd have fixed this age-old "bug" regarding not accepting modification times long ago.In my opinion it would be more consistent, if the date check after copying behaves the same way as the check when doing the "Compare" operation. This means that if I have set the "Ingore time shift" field to "1,2" the warning should not appear if the dates differ only by exactly one or two hours. That's what this setting is for after all, right (i.e. a workaround for the problem with different time zones, as far as I could defer from the documentation)?
MTP returning a different time than what was set only milliseconds before is simply yet another "bug" and has nothing to do with time zones or daylight saving time. OTOH there's nothing the user can do about it, so it would be nice if this particular warning was ignored when "Ignore time shift" is set. However it seems simply permanently ignoring the warning is a good enough solution.