Unable to recursively process files with a given extension

[GitLang]

Maybe I am missing something, but I find the the -r recursive mode with work on all files in the directory tree, but not on a desired subset, such as *.hex or file.??. The manual file is ambiguous 👍

   -r     Enables recursive mode. All subdirectories are traversed. Please
          note  that recursive mode cannot be used to examine all files of
          a given file extension. For example, calling  md5deep  -r  *.txt
          will examine all files in directories that end in .txt.

It says it cannot be used for that purpose, then says it will examine all files passing the filter.