I am always surprised to see how frequently bottle ejection issues come up. I have a small sample size of myself and those I ride with, but I just dont see bottles being thrown from cages. The cages I use are either some BrandX cages I bought from Wiggle for like $2 each or some stainless King cages. My kids and wife have cheap aluminum cages or some cheap plastic resin cages- they hold. The cheap aluminum basic design is on a few dozen bikes I help maintain for teen cyclists each year.
Bottles ejecting just isnt an issue for the various cages I come across.
I ride a bunch of gravel and never think about my bottles flying out of their cages.
Are people using really quirky bottles that dont fit well? Are they bending their cages open for easier access? It will forever be a mystery, I am sure.