I think the "upgrades" are real to an extent. BUT, it has to align to your priorities.
Harley, (and every other manufacturer) is balancing cost, EPA, mileage, comfort, usability, etc. So, they compromise a bit on just about everything.
In this case - polyurethane or more specifically "graphite impregnated polyurethane" bushings have been big thing in car suspensions. I've changed out bushings on 5 or 6 of my cars and replaced stock rubber bushings with these. Were they better? Not for comfort. That's for sure. Road vibration and "feel" was much higher....I was going for improved handling AT THE EXPENSE of comfort.
I know Harley uses rubber to help isolate vibration. Rubber is going to have more play (thus the isolation) than a polyurethane bushing. So, it depends on whether or not you value handling or comfort.
And, while the cost may seem insignificant on a single bike (or car) once you multiply it by all the bikes produced, it gets expensive. Ford sells ~700k F series trucks every year. If they have a part that costs only $1 dollar more, it's nearly 3/4 of a million dollar hit.
I recently bought a BMW with the B58 engine (3.0l turbo). From the factory, it has 375hp and 375ft/lbs. There are five or six chips you can buy that will add 50 to each of those figures in about 5 mins. And, if you tune AND replace the restrictive downpipe you can easily get 500hp at the wheel.
BMW knows this. They could easily do this. I don't think it even compromises longevity. But, they'd never get the Corporate Average Fuel Economy (CAFE) they need and may not pass emissions in places like CA. Neither of those two things are important to me....but, they are critical to the company.
Harley is sort of the same. They compromise to meet objectives that differ from mine. I didn't realize that was going to be $10k + different....but, here we are. I've replaced a ton of stuff. Some was worth it, others not so much.
But, the "tinkering" is part of the hobby for me.
My approach from this point forward is: I will upgrade as I need to replace. So, when parts start to fail, I will look at the best option even it's more money. At that point, I need to spend some to get back on the road anyway, the decision is then only about the incremental. (which usually isn't terrible).