This isn’t always true and it’s not always obvious.
For example with imaging - axial slices of the patient through symmetrical structures. The brain, lower abdo, a single leg or arm etc, etc. There are conventions in image display for a reason - it is not obvious.
For axial slices, as an observer, you are positioned as though at the foot of the patient’s bed. Your right is the patients left.
Greek dexios and aristeros ... well dexter come from dexios", as does the chemical suffix -dextrin. Aristeros* is a euphemism, it means something like "best" (I wonder if that's the origin of 'put your best foot forward') ... I'm told that left-sided things were unlucky to the Greek speaking peoples and Greek language apparently compensated by describing that position positively.
It's an interestingly deep rabbit hole in language etymology just how much "left" gets besmirched and "right" gets positive connotations. (The fact that "right" is also a synonym in English for "correct" being another bit of evidence.)
Don't make assumptions, codify it.
The orientation is screwed up and images should almost never be displayed like this.
If the patient’s organs are in non-standard locations (situs inversus, dextrocardia etc), something very bad will happen when orientations are messed with. Use standard orientations and label the images.
Your point was well made.
I'd also assume it would be simple to spot just because the image is always took from the same direction so the narrow part points out to front/back of the patient