As written in my linked guide, if you install MiXplorer busybox, keeping timestamp works fine for copy and move. Using toybox there was always some timezone problem. Doesn't it behave the same for ftp and other client/server communication? Both sides, as server and client? Would have guessed that it calls touch in the same way.
Nice guide!
Unfortunately, even using busybox (either the one MiXplorer installs or the one available through Magisk) timestamps are only somewhat correct. MiXplorer FTP server sets wrong year (but right month/day), wrong hour/TZ, and seconds also seem to be missing (maybe a FTP limitation, but I didn't check it).
What puzzles me is how other apps (SambaDroid or Samba Filesharing come to mind) manage to process timestamps flawlessly. I find myself copying files through FTP (for speed) and then adjusting timestamps using SambaDroid and some timestamp sync software...