And the problem is...?

I'm certainly missing the issue here. IUPAC is concerned about misleading terminology (doesn't make just a horrifying lead in?) in this case (open access) the term "polydispersity index". Huh? I never knew there was a problem.

Certainly there is some logic to the case:

"Monodisperse’’ is a self-contradictory term and ‘‘polydisperse’’ is tautologous."

...but is the existing term really that confusing? Is that tautology driving someone insane? Worse yet, the new definitions that are proposed all use the Unicode 0110 character, "Capital D with Stroke":

The general symbol Đ is introduced for dispersity to avoid confusion with the conventional use of D for diffusion coefficient.

That's going to go over well isn't it? Or do you just think that people will keep using "polydispersity index"?

How well have they done with previous interventions? Look at what they came up with for "inherent viscosity" and "intrinsic viscosity": "logarithmic viscosity number" and "limiting viscosity number". Yes something needed to be done as both "inherent" and "intrinsic" can be confused especially when abbreviated as "I.V.", but the new terms are being ignored. A Google Scholar search for use of "intrinsic viscosity" from 2000 to 2010 yielded about 16,000 hits while a similar search for "limiting viscosity number" yielded only 450. As suspected, that term is DOA and the same will be true for "dispersity".