I think thats the thing; these things aren't merely units of measurement for practical purposes, they are also cultural, almost akin to language. Phrases like "In the 90s" for temperature, "extra yard of pace", "strapping 6 ft man", "go for a pint", "pound of flesh" etc..they are all kinda ingrained which is why you shouldn't mess with it all too much, and it's a mistake the EU did make back in the day.
In practice no change of note will come from this, it's probably a small change to a piece of legislation that recognises two systems. It won't lead to much change at all, but recognising it is probably the right thing to do.