bash Noob: What's wrong with this line?

I’m trying to make a bash script written for BSD work on Linux, in case that’s relevant. Now I’m stumbling over this line:

json="$(sudo -u "${vpnUser}" -- curl --interface "${adaptorName}" --get --insecure --silent --show-error --fail --location --max-time "${curlMaxTime}" --data-urlencode "token=${authToken}" "https://${gatewayAddress}:19999/getSignature" | jq -Mre)"

I’ve echo’ed the values of the variables from the script and they look fine. Then I replaced the variables with the values. Then jq seems to complain about a syntax error (generic Usage: output) and curl, I assume, says (23) Failed writing body.
If a just run the command like sudo -u ... | jq -Mre it prints what looks like a JSON file.

Never mind! I got curious why the author would pipe the output through a parser which basically doesn’t do anything to the data, it only formats it into a more readable, multi-line output. And I assume that the multi-line format is the problem here? Removing everything after | helped.

Now another question: does anybody know if the original version is supposed to work with a BSD bash? Or should I tell the author (which states "…specifically in FreeBSD" in the comments) about this?