Why are you scratching your head over this? You come out with a post, slamming the intelligence of several thousand knowledgeable shooters, and then have the guts to act surprised
Ask questions here-you are going to find a huge reserve of knowledge on this site and many, many people with decades of experience visit here every day. I don't always post every day, but I know that I am going to find a correct answer to my questions, and can freely share what I know with others.
Take your post and turn it around-why would anyone use a 12 gauge blunderbuss on a little bitty quail? Gee, it might be the only shotgun they have, or any number of very good reasons. No doubt the mighty 12 is the most versatile shotgun gauge out there, but the smaller gauges have their place too.
I have used 20 gauges on deer with slugs, and also on pheasant and none of them scolded me for using a "stupid" gauge. In fact, they all died just as quickly as if they were bopped by a 12.
The nice thing about that 870 LT is that it is lighter for all day carry, and at least in the case of the 20, a 3 inch 20 packs as much shot as a field load 12 if thats what you need. The disadvantage being a longer shot string.
My utmost respect goes out to the scattergunners using a 410. There's a lot of folks who buy that gauge for their kids as a beginners shotgun, but unless there is a physical strength issue, the 410 is probably an experts shotgun. On the flip side, if the youngun can hit it with a 410, they can hit it with most anything.