If I should do anything on a transfer arm, it is news to me. The parts in it only move when I shift gears, that is not a lot of movement or wear. Also, I would not be surprised if some of the lube oil in the hub got into that transfer arm during use and regular riding.
I changed the oil in my hub before I went to Iceland. I suspect that the wheel was in the cargo area with the left side down and I suspect the air pressure changes caused a lot of my lube oil to leak out of the hub, possibly into that transfer arm. The photo will tell you why I suspect this. But all last year I never had that mess of oil on my EX box or transfer arm, so I think that lube oil loss in Iceland was a one time event from the airplane.
For comparison, my Sram Dual Drive (a three speed internally geared hub that takes a cassette) was greased at the factory and is only supposed to get a few drops of oil a year. I put 360 miles on that hub last week. My point is that it is pretty easy to over-think some of this stuff. If they do not tell you to maintain it, I am not going to worry about it.