Precisely this. It's even down to the logistics of every tiny thing. Mine don't have swimming lessons because it's one adult: one child ratio and I can't be the adult in the water simultaneously for both of them.
I remember when I put DTwins in reins, and eldest DS was cringing "omg mum, you look like you're walking two dogs,"..."thanks for that DS, it's to stop them both running off" ..."can't you even run fast enough not to have them on a lead?".... "Why yes, DS, except it doesn't matter how fast I am, I can not run in two directions at the same time."
Is your baby waking you every three hours? While your two year old sleeps through? Super. My babies wake up every 3 hours too, but not on the same schedule. So the one that wakes at 1am, that's fed, and changed and back down, settled for 1.30am, I then hopefully fall asleep by 1.45am and boom, 45 minutes later 2.30am, here's twin 2, fed changed and asleep by 3. Me by 3.15....oh, hello twin 1 at 4am.
My particular favourite is 2x vaccinations. That's a both of you take the day off work job.
The only saving grace to the bunch with their "2 under 2" nonsense, is that until you experience it, the extra stuff we have to do/stuff we can't even attempt, isn't instantly obvious, so whilst they're clueless, it's not intentional. Some people genuinely don't process any further than, "twins, so that's basically just a double buggy instead then"