I thought 1 to 2 was a bigger leap myself. You went from being able to hand off the kid and take a break to handing off the baby and getting the toddler in return.
To use your "man-to-man vs. zone" analogy, going from one to two is like going from playing defense to playing both sides of the ball. Sure, going from two to three, more stuff gets missed, but the exhaustion level and overall work load didn't change that much (in my experience).
Then again, maybe it's more about the age of the elders. We had two in two years and then didn't add the third until the big kids were 6 and 8, so they had already gotten the hang of basic life skills like getting dressed for school, getting themselves breakfast, reading, etc. Maybe that's why 3 to 4 was easier for you and 2 to 3 was easier for me.
It sounds like the adjustment is a bit rough for you at the moment if you feel like 2 sentences became too long. Don't be so hard on yourself mate.
Becoming a dad is a shock to the system but one gets easier. I think more than one is relentless, there's just no break ever. And they act like force multipliers, they drive each other mad and amp up the intensity where 2 is more like 2.6.
Zero to one was a shock, but we knew people with kids and were as ready as you can ever be for your first.
One to two was easiest.
Two three was a bit hard as it was a reset on what we could do as a family.
The hardest was from three to five. Twins are hard. It's like two kids at once! Also now we can't move in a single normal car. At first, because it wasn't just a family of seven, but a double buggy and all the stuff you need for babies, we just got a massive Transit. Literally a bus of kids.
They twins are now five, at school, and we just gone down to a normalish seven seater. It's still overwhelming at times. If we come to visit, I feel we are over overwhelming our hosts.
I see families of fours kids out sometimes and think "That's a lot." And we have one more that!
You just have to deal with it. Least all of ours are healthy with no conditions to manage. Many families with less kids have it harder.
Obviously going from zero to one is... otherworldly, but to some extent you expect everything to be a bit crazy for a while.
Going from one to two was almost the opposite. We figured we had this front to back....nearly two years on and he's still not slept through the night, and me and mummy are still struggling with the day to day adjustments we had to make for the second; new job with new working hours (Goodbye night shift, hello 50 HR a week jobs), and the fact that I've not slept in my own bed in well over a year at this point.
Contrary to popular sentiment, I'd say it's not the numbers - it's the age.
For my wife and I, babies are easy. Toddlers were way more of a challenge. But for most of our friends they found it the opposite.
I've heard people say before 1 to 2 is harder whilst 2 to 3 is simple, and in this thread 2 to 3 is harder, etcetera. I'd wager a big part of it is 'when' you add each new child, relative to who your other children are and what they are needing at their current developmental stage.