As a former postbac from a top program, I'd also add that in addition to tightly integrating everything, these programs make the courses substantially easier than undergrad equivalents. They do this in two ways: (1) by removing non-medical stuff from the curriculum (e.g., plant biology, calculus-based physics) and (2) by making grading easier.
As an example, the two semesters of organic chemistry + lab I completed at my postbac had an average grade of an A-. In addition, in all of the lab components, they didn't care how much yield you got on your practical experiments. (Perhaps some individual courses are like this in undergraduate DIY coursework. Frankly I wouldn't know since everything I know is all hearsay from friends.) All-in-all, the postbac was very chill.
My bigger point is that if you're deadset on doing this in one year, you should seriously consider the top programs (Bryn Mawr, Scripps, Goucher) because if you get in your odds of getting accepted to med school either through a linkage or after a glide year are >90%. Also, your time doing the program will likely be easier than if you had done it all in regular undergrad classes. Here's a helpful list of the top programs with their rates of admission to MD programs and the percent of student attrition -
Best Premed Post-Bacc Programs for Career Changers (2022) - PERSONAL PREMED
Obviously, this route is more expensive than the DIY and it's not for everyone. But it should be considered if you're trying to maximize speed, minimize difficulty of coursework, and maximize outcomes!