As explained and shown on the picture I posted, on the R&M Birdy 3 Touring the derailleur cable+housing uses the bottom output opening of the main frame, the bottom input of the swing arm and comes out from the same output opening as the derailleur cable+housing of the picture you posted.

Since I changed the derailleur to an 11s Ultegra, I had to remove and replace the derailleur cable and I discovered that the housing coming from the shifter stops at the special rigid, spring like housing connected to the rear swing arm that goes to a stop inside the front end of the swing arm and the short housing from the rear output of the swing arm to the derailleur goes to another stop inside the rear of the swing arm.

Since there is a stop inside the rear end of the swing arm, I do not understand how a one piece housing could go thru the swing arm and come out from the same hole of which the short housing+cable comes out on my Birdy?

Some times ago, you already asked how the cable+housing for the rear SA IGH is going thru the rear swing arm and to answer your question, I inserted a cable from the top front input of the swing arm of my Birdy and this cable went out om the bottom more or less in the in the middle of the swing arm just like the cable+housing of the IGH of your picture.