Exclude feature fails for files and database tables when cli is activated

Issue update: we have determined that the exclude feature fails for files and database tables when cli commands are activated at least in some server environments. The question now is whether to try to fix the problem or perhaps eliminate the exclude feature, given that many larger sites are moving to other options for backups while it is the smaller sites or sites on shared servers that are relying more heavily on the Backup and Migrate module for Drupal 8 going forward. Since it appears that the problem could be related to the server, not the module, this issue could be difficult to pinpoint. A problem with eliminating the feature is that cli commands and file exclusions really are faster if the server supports them for backups. Here is the original issue summary:

I am setting up a profile for backing up the Public Filestore, and entering a list of directories to be excluded. The help line says "A list of files or directories to be excluded from backups. Add one path per line relative to the directory being backed up." Entering a path such as "abc/xyz" does not work. If I enter "xyz" the directory "abc/xyz" is excluded. (Fortunately I only have one "xyz" at any level, so the workround works for now.)