It cracks me up when people get so touchy about an Estes-level construction step just because it involves propellant. L3 certs require electronic ejection, which is way more involved to learn, calibrate, and master than coating a piece with glue and sliding it into a tube. The oversimplification of the motor process is a disservice; R45/curative is the right way to glue in grains, especially for flights with high g-loading, but I'm sure the reason this isn't done is so people don't have to "figure out equivalent weights." It's a ratio, like mixing epoxy on a mid-power rocket. Come on, people.
The amount of rudimentary skills people need to acquire to build a rocket to fly motor that "requires" gluing the grains (hint: it's good practice on every motor) far outweigh, both in number and complexity, the knowledge required to bond grains.
What it comes down to for me is this - you don't see Estes RTF-type rockets being sold in L2 and L3 size (though, to be fair, the slap-it-together fiberglass kit craze comes pretty close) because successfully flying a project of that size requires more engagement than simply purchasing something. How is it that we don't apply this logic to commercial motors? It blows my mind when I see people flying extreme projects (min dia N5800s) that don't know the FIRST thing about motor design, manufacture, or functionality. I rest my case on all the threads on here with people asking how to glue the grains on their N motor (I've yet to see a thread with someone asking how to glue the fins on their Ultimate Wildman).
I'm sure you'll vehemently disagree with me, but it's the mentality like the one you've posted that proliferates this problem. "Just saying"