ERP5 SR uses both of them, and without dedicated handling nxdbom breaks as

    AssertionError: (PkgInfo(name='readline', version='8.1', kind='', url='http://ftp.gnu.org/gnu/readline/readline-8.1.tar.gz'), PkgInfo(name='readline', version='5.2', kind='', url='http://ftp.gnu.org/gnu/readline/readline-5.2.tar.gz'))

readline is the only item that ERP5 SR uses with multiple versions.