Is winning by submission a TKO?

I'm curious, is winning by submission in a fight considered a technical knockout, or TKO? I've heard some people argue that it's not because the opponent is voluntarily giving up, not due to being unable to continue. On the other hand, I've also heard that since the opponent is unable to defend themselves and has conceded, it effectively ends the fight in the same way as a TKO. What's your take on this?