Do they define if this relates to anything noticeable in your day to day?

For example, I can put my right hand above my shoulder and left hand near my lower back and easily connect both hands behind my back with fully interlocked fingers by converging in the middle. They reach to the other hand's palm.

But I can only barely touch my fingers with both hands if I switch it up so my left hand is up top.

I have no pain or day to day mobility issues but something is lopsided. Is that what they consider abnormal?

Limited range of motion on one side could cause some deviations in scapulohumeral rhythm, so your force application won't be optimal and may cause injuries, or even cause uneveness and side effects in gait cycle. And with time it tends to get worse since the body would be trying to adopt to execute the function. But suboptimal force application eventually would cause joint injuries if a convex (humerus) is rolling without gliding or vice versa or doing it in suboptimal rhythm.

That's my personal take, not a doctor, study kinesiology as a hobby.

All such minor mobility issues could be addressed by body conditioning excercises including simple isolated mobility drills to learn range of motion of joints.

I'd consider it abnormal that you can do that; I can't get my fingertips within a foot of each other doing that.

I'm nearly 60 but I don't know if I could ever do that. You have good mobility IMO.