Re:tyre rotation conundrum

I still have the original "new" Duceller as my spare. I have fitted it once in an emergency, it worked fine with my current AT, did about 100miles  on tarmac, and it's now back on as a spare. So I wouldn't be too concerned about keeping it in step with the main tyres, it's only an emergency item for me.
MY spare is in perfect condition as I have a cover that keeps the sun off it, so I personally don't see a need to involve it with tyre rotation. To be honest I don't even rotate my AT tyres, they are much the same when I check them so don't see the need with my driving style. 

When i had my Jimny I did 5 tyre rotations to avoid any diameter difference problems and also in expectation of replacing all 5 with ATs at some point. Now I have a subaru, they seem to be sensitive to tyre diameter changes too (Subaru suggest maximum of 2/32" diameter difference across the same axle) and it seems common in the USA that they'll get a tire dealer to "shave" a new tyre down in diameter to match the other 3 or 4 tires if a new one needs to be fitted to replace an unrepairable tire. Not sure if shaving tyres is a thing over here?

Is the Subaru a permenant 4 wheel drive? In which case I susect it is the same reasoning as the Freelander in that any difference in circufrerance means a difference in rotational speed of opposing tyres and hence potential to screw up the transmission through wind up - or something along those ines!

I often think "Am I the only Jimny person who is doing all this tyre rotation every 6k miles"?

The dealers don't ask or appear to do it and as others point out the spare on most Jimny's often has the unused look to it after many years of service.

Now I've done the 5 tyre rotation every 6k miles for over 30k miles and friends and family think I'm totally bonkers! How many Jimny owners do you think bother either doing it themselves or pay the garage to do it as an 'extra' to their standard service? Still it gives me peace of mind and a chance to make sure that my wheel nuts are all correctly torqued.

I did! Back when I was expecting to keep the Jimny for a longer time, I did the 5 tyre rotatation every 5k miles up until just over 3 years and 30-something K miles.
I follow an American forum and they're obsessed with changing oil and filter every 3-5k miles or so and at the same time getting all the tires rotated. Main dealer cost seems about $75. I've been quoted £166 just for the oil & filter!
No spare in the subaru so rotating the tyres is a bit of a challenge with only 1 jack.

I am doing it, bit for me that is only once a year diluent to the milage I am now doing.