When the lines are terminated with CR only, most terminals print the lines over each other, which means, when they print a CR, the cursor jumps to the beginning of the same line. So, you probably did not get "the latest key-value pair", but all, but you could only see the in the terminal the latest.
All munin versions i know of work fine with the output of the script. Was your question just just out of curiosity, or did you actually observed an issue? For debugging of munin output, one should use "munin-run PLUGIN_NAME".
Nevertheless, i have changed in git end-line termination to CRLF, it seems, that everything continues to work.
