Tubeless Tyres -"saying the same things about tubeless tyres over and over again" Hippy read the first f**king post

What's the reasoning behind it ? Having the latex stick around the flakes to help seal breaches?

Yes. Sealant manufacturers need to strike a balance between effectiveness, longevity and ease of install. Environment friendly is also a big factor. By upping the size and / or number of the particles in their formula, they get better performance but ease of install and longevity goes down.

By adding glitter you are upping the particle size and number dramatically, so the effectiveness of the sealant rises as it helps the sealant form bigger clumps, quicker. It's likely that this decreases longevity but I'm not aware of any conclusive evidence, I mean, most people like to ride their bikes not measure how long it takes sealant to gum up in a tyre.

Glitter aint great environmentally because it's plastic particles and that shit never goes away, whereas stock sealant is designed to degrade. Unless there is some bio-degradable glitter around? I've heard of people experimenting with coffee grinds and pepper...

But you could argue that's a bit moot given that there's so much in a modern bike that's a horror show for the environment.

It's harder to install because, as above, you can't inject it to an already mounted tyre, which in my experience is the hassle free, mess free method of getting sealant where it needs to be, and not splattered all over your house / yard.

Anyway, add glitter, seal bigger holes, make a bigger mess if you are unlucky is the TL;DR.