There is really no conspiracy to hide FJR flaws here!! This is NOT a major issue or a failing with the FJR. In 183,000 miles, I have experienced handlebar wobble exactly twice. Both times, it was immediately fixed by replacing a well-worn or scalloped front tire.
Perhaps the FJR is a little more susceptible to tire-induced wobble than other bikes due to geometry? Quite possibly people are not making sure everything is aligned properly after changing tires - see the following from the FSM.
CAUTION:
Before tightening the wheel axle bolt, push
down hard on the handlebars several times
and check if the front fork rebounds smoothly
Should there be a mechanical advisory on this? Maybe - if only to tell people that wobble is most likely tire-induced and that keeping inflation higher than the manual suggests will help with wobble, handling and tire wear (IMHO). Shouldn't have to tell people to follow the FSM directions when installing a wheel but the failure on behalf of the mechanic somehow becomes the fault of the bike/manufacturer. Installation of tapered steering head bearings is a Band-Aid approach that a number of people have used and it has served to suppress the tendency to wobble in some instances.
On the other hand, there's lots of information on this forum and not at all difficult to find references to this. By the way, something being banished to NEPRT doesn't make it go away. Some of the best reading on the forum is found there.
Claim: The FJR is prone to low speed decel steering headshake. (Wobble)Support: Dozens, maybe hundreds, of rider complaints across multiple forums.
To address your claim it is maintenance error.
I have maintained my six bikes over 30 years and 248k miles.
Only the FJR wobbles.
I have a 93k Aprilia that needed new steering bearings, but never wobbled.
My FJR wobbled on it's factory set of half worn tires.
I have run tires ragged on my Ducati, Aprilia, Victory, and Suzuki,
and yet no wobble. Only the FJR wobbles on more than half worn tires,
even when inflated to 40/42 F/R.
I have followed the suggested FJR FSM front end assembly. FJR Wobbled.
This forum suggested replacement of the bearings to tapered bearings made a great improvement. Now the bike doesn't try to kill me when I zip up my jacket mid ride. Yet, with a pillion & luggage, I can still feel the decel instability in the bars. Overload the Aprilia Futura with pillion and luggage, and it handles like a pig, yet it does not have decel headshake.
The three bikes in my local circle of FJR riding friends all wobble.
Two are dealer maintained.
So if it is indeed maintenance error and not design weakness,
the procedure is either obscure or finicky.
Addendum: My apologies for whipping that horse, again.
I have been eyeing a soon-to-be-leftover Black '17ES,
and the disclosure that ES's wobble too squashed that dream.