sysroot and coredump debugging

Hello,

I have an target system, for which I have a sysroot path in my
development computer. Both GNU/Linux.

I expect that I can run this in my development computer, after downloading
the core dump from the target system:
(gdb) set sysroot /mysysroot
(gdb) file myelf  #  it has debug info
(gdb) core-file core

And this never works; it drops the file with the symbols, thinking it's
unrelated to the core dump:

warning: Can't open file /home/user/myelf during file-backed mapping note
processing
warning: core file may not match specified executable file.

Nothing works with dynamic libs loaded either. The only way I can make gdb
to allow me to debug the core dump with symbols is by copying the elf to
"/mysysroot/home/user/myelf", as it was in the target system.

Is this expected? It is very annoying. Why should the elf of the
executable sit within the sysroot in an exact place, to debug a core dump?

I use gdb 15.2 but this happens at least since gdb 11. Maybe it is fixed
in a newer version?

Thank you,
Lluís.