jcmd <pid> help JFR.start
lists 'path-to-gc-root' option, however, the actual option name is 'path-to-gc-roots'

The same holds for JFR.stop documentation. Also, in the examples to JFR.dump command, there is a line with two typos:

$ jcmd <pid> JFR.dump fillename=leaks.jfr path-to-gc-root=true

Note "fillename" and "path-to-gc-root".

The manual page for "jcmd" (man jcmd) also mentions 'path-to-gc-root' instead of 'path-to-gc-roots'