For me the top plane is very important but the one on the right or the front, everyone has their own opinion on our equipment and no one ever agrees.
So for us it is not important. Which may explain why I had never seen this detail. (for me!)
The top plane is supposedly the ground so indeed, no ambiguity.
For the other shots, as Perceval would say, " The north, depending on how you are shot, changes everything ".
But in absolute terms, we are entitled to consider that the front plane is the room seen from the front. Especially when you are looking for harmony and coherence between the parts, especially when they are intended to be exported in identical positions and references.
After for the right-hand plane, it's much more debatable; It's seen from the point of view we have of the room when we turn around to our right (counterclockwise), when technically it should be a view from the right side of the room...
You're going to tell me that I'm lousy, but this solution, if it's not stupid or devoid of interest, forces me to reassign sketch shots and other relationships, which doesn't delight me too much. But it may not be the worst...
be careful, what you have circled in Blue is to symmetrical " by reusing " the object with the center of gravity positioned symmetrically, but you will always have the same part, the last one creates the symmetrical part (like your left hand and the symmetrical one of your right hand, while the first 4 is your right hand "rotated 180°" in space! along a different axis.
As for the positioning, whatever the plane chosen, the result (even in SW2025SP2) will be a symmetrical one positioned in front plane in your own piece because the developers must have thought to themselves! We don't care about a symmetry following any plane, even inclined will give the same results, so! Let's keep it simple! Thank you DEVs. 2 bucks of SW that still bring out nuggets without having them tested by real users to understand their expectations!
Similarly this famous body-move/Copy function (which is not the one for which you have the accessible icon) that you can't modify or create without going through an ASM that you delete afterwards!! great art!