I am glad you asked this question, because I have always wondered from the first time I took suboxone. Why does replacing a full agonist with a partial agonist produce a worse withdrawal than having a full agonist leave the receptor completely.
First time I took subs 24 hours as asked. Next time 18 hours next time 14 and so on until I was only waiting 2 hours. And it still worked - kind of. It at least didn't make the withdrawals any worse. I was almost convinced same as you. I even thought maybe I was a special case.
Then one time I tried taking it 10 minutes after taking fentanyl. It was the worst thing I have ever experienced in my life by far, and I have withdrawn from heroin, have died and spent 3 weeks in the hospital, been hit by van, drowned in a pool, tripped on mushrooms alone in a snowstorm with no way way home, precipitated withdrawal was worse than all of them combined and quadrupled. I was in a literal pool of sweat, no part of my body could stay still, my eyes were red and sore from crying for hours, I was hallucinating people and things, I stuttered and mumbled as I forced myself to speak one sentence to my girlfriend. I KNEW opiate withdrawal couldn't kill you but I still wondered if I would be alive by morning. You have a valid question, and you are probably right that 24 hours isnt necessary. but precipitated withdrawal is real, I promise you.
As for WHY - I still wonder myself, sorry.