I appreciate the importance of what you're seeking to establish here. My argument is not that we / you shouldn't reformulate our language (the conventional terminology is fraught with many difficulties, especially the ones you cite here) but I'm not sure "People of the Global Majority" doesn't have its problems as well. (The advantages of the term PGM as you describe them are for me undeniable.)

Here's the catch: If you create a category "People of the Global Majority" then there is obviously another category "People of the Global Minority," and in this context, that group would be what we now call "white people." Now technically, any ethnicity / race is a minority (at most a plurality) if taken individually. So the defining factor for PGM is their non-whiteness. In other words, even though white people are in a minority, their status is calling the shots when we establish categories.

If it's clear in a particular discussion that the participants are discussing race, but want to do so in general terms, a more appropriate division might be "Enlightened People" and "Unenlightened People."

Almost a century ago, W. E. B. Du Bois observed that black people in America had two souls (identities): as black people and as Americans. Du Bois didn't say this, but I believe that white people in America (for the most part) only see themselves as having one identity: as Americans. For them, whiteness is not only the default race; it is the defining consciousness of the country (and world,, for that matter). Black people know what it is to be white; white people for the most part don't know what it means to be black.

(Aside: after the death of George Floyd, many white people are beginning to understand the nature of systemic racism; they are starting to know how real black victimhood is. But that doesn't mean that they understand other aspects of blackness.)

In what we now call the postcolonial era, the group you're calling PGM has a pretty accurate picture of what it means to be white. But in spite of the great diversity of news and entertainment today, white people as a group (world-wide) don't know what it means to be non-white.

So MOST white people would fit in the category "Unenlightened People." And MOST of the rest of the world could be described as "Enlightened People." This reformulation has two advantages: white people who through empathy, determination, and hard work learn significant truths about any / all other ethnicities would be classified as "Enlightened." (Of course no one thinks of themselves as bigoted--whether you're classified as enlightened or not should depend on how others see you.) The second advantage is that those very few non-white people who seem to misunderstand what it means to be black or white or whatever (like Tyrese Gibson recently) don't get a free pass just because of their parentage.