unexpected behavior of cp and mv

[Alberto Sentieri <22t@tripolho.com>]

cp and mv are not preserving the file timestamps when copying from a 
ext4 file system to a smb file system.

I am running cp and mv on:
$ lsb_release -a
No LSB modules are available.
Distributor ID:    Debian
Description:    Debian GNU/Linux 10 (buster)
Release:    10
Codename:    buster

SMB is running on:
$ lsb_release -a
No LSB modules are available.
Distributor ID:    Debian
Description:    Debian GNU/Linux 9.12 (stretch)
Release:    9.12
Codename:    stretch

I am using "cp -pi" to copy the files and "mv -i" to move them.

If I run cp or mv on a Debian stretch, time stamps will be correct on 
the SMB file system.

Buster gnome3 file manager will copy or move the files without problems, 
I mean, they will preserve time stamps.

This started happening since I upgraded my workstation to buster, so the 
problem seems to be in buster. I am mounting the file system on buster 
with the following line added to fstab, which, by the way, is the same I 
was using when my workstation was running stretch:

//192.168.1.2/alberto /mnt/u1/rw cifs 
credentials=/root/pass/alberto.pass,uid=alberto,gid=alberto,rw 0 0

Does anyone knows which package is causing this behavior?

Alberto