Abruptness of Deacceleration/Engine Braking

Not a problem for me - I'm not your typical Harley owner. I've had my bike almost 8 years and other than a slightly taller windshield, it's completely stock. I always ride with a full-face helmet and ATGATT. I've enjoyed my Sport Glide, but it's the last Harley I'll own.
 
The nice thing about a 2023 R3 is it can be tuned with TuneECU very simply. The jerkiness you experience can be tuned out very simply. If it is the tune and not the rider.
 
Take another test ride, only this time put it a higher gear at cruising street speed before you let off the throttle.....
I think the solution is what @mo8414 and @atomsplitter have recommended. Just cruise in a higher gear/lower rpm. I guess I'm so used to it that what you've described has never bothered me. I use engine braking a lot. Changing the tune has also been recommended- do it! Penner's Tune specifically. Don't think that will be the solution to less aggressive engine braking, but it will be the solution to taking what seems like a big fast bike and making it even torquier. What I experience, and it could be remedied with tuning, is the opposite- a pretty snatchy throttle at the lowest RPMs that you have to be mindful of coming out of corners to keep the front end from rising. I'm just "careful" .

Where are you in NC? I'm just east of Asheville. Let me know if you want to ride.
 
Regarding my initial surprise at the abrupt deacceleration, traffic was pulling away from a stoplight and moving well, then we got caught quickly by the next stoplight and everyone hit the brakes. This happenned a couple more times before I got on a less busy road. I would have only been in 2nd or 3rd gear each time. I'm sure my right wrist muscle memory responded naturally - just not appropriately for the Rocket. Nothing more saddle time won't correct.

Journeyman, I live in Cary, near RDU airport. I'll contact you next time I'm gonna be out your way. Thanks.
 
The actual delta between your Harley and the Rocket is the drive train. If memory serves the Harley is belt driven and the Rocket is a shaft. The amount of play in the belt (my '13 Thunderbird Storm is belt drive and a 1700cc parallel twin) allows for some give on the engine braking while the Rocket's shaft is coupled to the crankshaft and immediate. Once you get used to it there will be less angst. Also, the Penner tune is a must for smoother throttle response regardless of riding mode. If you don't have a TuneECU setup and license it's not expensive and there's plenty of help available here and on YouTube to get you sorted out.