Usually people's view are 'if it isn't broken then don't fix it'. Honestly, I'm part of that camp. I wouldn't mind it left as it is now. Even without the X:_Y:_. That addition is obsolete since the position listed in <pos> and on your map already indicates your current location. From that point you can just deduce what the first number and second number means. Basically addition of X:_Y:_ is for people who can't deduce <pos> meanings.
What's wrong with it is actually having to ask in the first place.
Before even <pos> funcationality came in along with the position details for your current location on the map, people would just go by whatever people said for coordinates and assumed it was read as (X,Y). However, I can say I've ran into several times were the directions I was given was reversed as (Y,X). And I ran to the location and only to realize it was on the other side of the world.
Was it wrong of me to assume that they were giving me (X,Y) coordinates?
Another situation was me giving coordinates to someone else. Who then asked, 'Up and left?' Which then I said 'yes, if you mean horizontal and vertical'. And somehow, they thought horizontal meant rows, and vertical meant columns!
Was it wrong of me to assume that they understood what horizontal meant x-axis, and vertical meant y-axis?!
Lastly, the situation I ran into my friend when giving coordinates, and wanted clarification. I said 'x,y'. Which was replied with confusion of what x and y was which I said the one running 'horizontal, vertical' which was still replied with more confusion, which then I had to clarify once more it's 'top and the sides'. Which then we both became flustered trying to just understand each other.
Was it wrong of me to assume that Cartesian coordinate system should be understood?
So, where does this confusion arise come from? Who knows, it really depends on how the person interprets information. It could be that they are thinking along the lines of reading latitude then longitude coordinates. Or maybe they just like reading the numbers off running on the Y-axis first before the X-axis. Or maybe they are dyslexics and mistakenly read it backwards.
But you know what, if it works 99% of time, then it's good enough. However, at least try to understand what is happening when it stops working at the 1% mark and see if there are any viable solutions to fix it.