The --odr switch is documented in dwz --help output and in dwz.1 man page: --odr --no-odr Enable/disable one definition rule optimization. Default value: Disabled. --odr-mode <basic|link> Set aggressiveness level of one definition rule optimization. Default value: link. But it is not documented that the flag is currently experimental (or what the limitations currently are).
Documentation patch posted: https://sourceware.org/pipermail/dwz/2021q1/000980.html
https://sourceware.org/git/?p=dwz.git;a=commit;h=3b4c8013f7f4f5e0cf31548bbacbf2d0f601da55