I am by no means a hydraulics, nor a Yanmar expert. However, in my recent research, it appears that many of the Yanmars have the ability to plumb extra hydraulics from the 3pt valve spool. It's not a "power beyond" port, but it does allow you to plumb without cutting the hard line.
I suspect that so many recommend cutting the hard line because it's much simpler to do that, than to try to explain look for this, then look for that, then, figure out what size plug you need to put in the inside of this port.
So, yes, I could very easily be wrong.
Here is a good thread, which has some pages from a YM model manual describing how to plumb in hydraulics. It talks about inserting the plug.
Check out page 2 for a pic of a valve spool with the "O" stamped on it. Page 3 has the manual pages
http://www.tractorbynet.com/forums/yanmar/43657-remote-hydraulics.html