I don't think it's a "tremendous" leap at all. I think #1 overall is definitely projecting some growth for him in 2024, but IMO you don't have to squint your eyes too hard to see it. I think you're underrating him a bit as a Texas fan because we've watched every minute of the growing pains so far.
Consider all the following data points:
His arm talent is elite and always has been.
He's young. This season will be essentially his true junior year. He turns 22 just a couple weeks before the 2025 draft.
By the time of the draft, he will have 30+ starts against high level competition.
Sark and Milwee have a documented history of developing QBs.
He more than held his own against top competition as a true sophomore last year. Quinn's 2023 COMP%, Y/A, and QBR (69.0, 8.8, 158.6) are a close match to Michael Penix's (65.4, 8.8, 157.1). As you know, Penix was just drafted 8th overall, has a very concerning injury history, and is 45 years old.
A QB has gone first overall in 7 out of the last 10 drafts. The only years they haven't are in major down years for QBs and an elite talent at EDGE goes #1:
2014: Blake Bortles 3rd overall, Jadeveon Clowney 1st
2017: Mitchell Trubisky 2nd, Myles Garrett 1st
2022: Kenny Pickett 20th, Travon Walker 1st
Modest growth over his 2023 performance would put his numbers right in line with recent top picks at QB. If he does that, stays healthy, plays well in some big games, and has a good pro day, he'll absolutely be right there in the conversation for 1.1. As we sit right now in April 2024, I'd probably handicap the odds like 1. Beck, 2. Ewers, 3. everyone else.