To make the problem more understandable to the people that are used to alphabetic scripts, suppose that tomorrow an Asian committee starts creating Uniword, a repertoire that maps complete words to numerical IDs. At a certain point they get to "colour".
Uniword committee: Well, that word shares meaning and origin with the other word "color", for which we have already a codepoint, so we will encode them under the same codepoint.
GB, Australia and Canada: Ehi! No! To us those are different words; especially, we do not want Mr. Colours to appear as Mr. Color.
Uniword commitee: No problem, just add some out-of-band information like "nationality" or "<span lang='en-GB'>"
"colour"-people: that will not work, there are so many cases in which this can go wrong. Whenever I copy a field from a DB I also have to extract this extra information?
Uniword: yes, that is the problem? C'mon!
"colour"-people: but do you need to do that in your applications?
Uniword: no, we have one code for every single word in our languages, including codes for very old languages that exist only in two palimpsests.
"colour"-people: and why cannot we have the same level of granularity?
Uniword: because you have too many words!!! And we started we had only 100k available integers.
"colour"-people: and now?
Uniword: now we have 2^32. But, yeah, that is not the point; just do how we suggest. This dialog is getting to long.
"colour"-people: "dialogue", please.
That was perceived as happening more than a few times in the Han Unification debate.
I remember being concerned about Han unification around the time Ruby 1.9 was released, since this seemed to be one of Ruby's major reasons for being encoding-independent instead of standardizing on Unicode. But I hadn't heard about this issue in a while, except to hear occasionally someone say it's not a problem (maybe it was a Chinese person instead of a Japanese person -- the Wikipedia page says that the Chinese aren't as concerned about Han unification since Traditional Chinese didn't get unified with Simplified Chinese).