Just my add my 2 cents regarding squatting and DL'ing:
I injured my back playing basketball in my early twenties. This turned into re-occurring lumbago events. 1-3 times/year I'd be suffering from it, i.e. for a couple of days I hardly could move, severe pain, etc. Really debilitating and scary stuff, especially given my young age.
Went to an oldschool doctor and he advised that the only thing that would really help was strength training. I researched and started squatting and DL'ing. This was about 15 years ago and I never had an issue with my back again.
Your body/levers are obviously built to load a large amount onto a straight bar and squat down and back up with it again. That is great. Mine certainly is not. Sure, of course I can squat. But can my body remain in position while balancing a bar on my back while doing so? Not correctly. Can I deadlift a straight bar without it having to either travel through my knee cap or slightly moving my back out of place to completely the lift? No.
How many others can say this and will get hurt like myself without knowing it until it is too late? How many others have no plans to compete in a power lifting contest and can get better benefits by doing ATG Split Squats v. bar squats and deadlifts and on top of better benefits (I have done both and it isn't a comparison in benefits for me) but also reduce the risk of injury greatly.
That is my point. If you are young and trying to make the football team, thus you have the right body type most likely, maybe squats and deadlifts are better. Most football players are shorter limbed and bigger bodied which makes them proportioned for DL and Squats. If you are a power lifter. If you are an Olympic Lifter. Sure, then DL and squats are staples.
If you are Joe Schmoe who wants to get stronger/better shape, especially in a more functional way, the ATG Split Squat is not just safer, IMO it is superior. You still get the full load, you still get the range of motion, you take out the injury risk, but you get more balance work (balance and equal strength in each leg) and you get more flexibility in the range of motion. I squated and deadlifted for years, squatted itself for almost 3 decades with static stretching, and I have never had this balance and flexibility.
My point isn't to throw shade on people who squat and deadlift. My point isn't ego driven. My point is when you get older some things happen and it is a very beautiful process. Your sex drive slows down, your bank account fills up, and the struggles of your 20's and 30's dissipate. And you start to think, what can I share with those younger men going through what I went through. What can I share with them that I know now that I didn't know back then. What do I wish someone had told me 20 years ago that I can tell a guy in that position now.
And certainly one of those things is that I wish I knew about this program 30/20/even 5 years ago. I feel like I wasted decades trying the big lifts and only ended up with back issues, which are going way thanks to this program.
And I am not writing this to change your opinion or throw shade. If DLing and Squating work for you, please by all means do it. I am writing this for the young guy, who is thin and long limbed like me and struggling in the squat and deadlift and is reading through this thread can see the opposite view. That they don't have to risk the injury to jump higher or get better leg strength.
If you don't know which to try, I would recommend trying both methods (a few months squatting and deadlifting and a few months with just the ATG Split Squat) to see what you like better. If you are not certainly which you are built for. Are you over 6' tall and mostly arms and legs and not a great natural lifter, though maybe good at back pulling due to your long leverage? I recommend ATG Split Squats. If you are stockier, with shorter limbs and a bigger torso, built more like an American football player or Rugby player, then DL and Squats will likely work great for you.