I suffer the same bug as GNU bug #31941:
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=31941

It says:
In Emacs 26, when moving a directory within a remote host over Tramp
using the scp/ssh method (e.g. with dired-do-rename or mv in eshell), a
copy and delete are always performed, even when a much simpler mv would
suffice. The behavior is the same when running emacs with -q

This situation is corrected in emacs 26.2.

My emacs version:
GNU Emacs 26.1 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.4) of 2019-02-03, modified by Debian

I'm using buster; (uname -a):
Linux desktop 4.19.0-5-amd64 #1 SMP Debian 4.19.37-3 (2019-05-15) x86_64 GNU/Linux

Thanks