memes

argument was that it was a more natural position to how we’d shit in the wild, in other words how we evolved?

Correct, and that argument is sound.

the position has better flow/use of the process you mentioned.

Here's where the marketing kicks in - better than what? Better than sitting upright like you would in a normal chair? Absolutely. Better than leaning forward to achieve the same relative anatomical position? Their sales pitch doesn't address this - by design.

never having used one I don’t know which is more comfortable.

That bit is subjective. If you like the feel of the SP, nuff' said, use it. I personally find it doesn't actually matter 99% of the time. Even sitting upright chair-like doesn't actually impair the process enough to make a noticeable difference. The only exception is the occasional shit-from-hell, like the kind that makes you feel like literal death from start to finish, but then once it's out you feel fine... which if you've never experienced, hopefully it stays that way; if you have, and are wondering wtf just happened, it's a vasovagal response to pressure and straining, and it makes you literally feel like you're about to die.

Our bodies are jerks.

Anyway, when that's happening, anything that can make the process even half-a-percent more efficient is a godsend, so I find myself changing positions a lot from the lean, to upright, to side-to-side, back to the lean, etc. Adding the SP to the mix certainly wouldn't hurt, but I don't think it'd actually contribute anything that other positions aren't already hitting.