I'm looking for feedback on Diamond Dallas Page's yoga program. I'm trying to A) get more flexible, and B) stop getting muscle twinges from sudden moments.

Seems like there is a good number of stories of people that gained a lot of flexibility and worked through old injuries with it.

I've never tried it though.

I've been doing it for a bit over a year.  I like it.  Like any other program you gotta stick with it.  There are three programs, basic, intermediate and advanced.  They're 13 weeks long, and there are usually four workouts a week.  It relies a lot on muscle tension to build strength, so you just don't go through the motions.  It's helped me.  I have a really bad right knee to the point my right leg bows out, and it's helped my flexibility and strength in my knees and hips, as well as my overall strength and flexibility.  I can squat down now, and even bring my butt to my heels, which I could never do before because of my knees.  There are different levels of individual workouts too if you want to do those.  Some are easy all the way up to extreme.  I've tried some of the extreme ones, and they'll kick your ass.  There are different modifications they show for movements if you're having issues, and like he always says in the videos, it's your workout, modify as you want.
He also likes to rename different yoga positions.  Child's pose is called safety zone, the warrior poses are called road warrior I, II and III, there's one version of road warrior called superstar, and so on.  The signature movement in DDP is the diamond cutter, which you'll do a lot of.  If you got any specific questions just ask.  It's better than I thought it would be and I'm gonna stick with it.

Should everyone start with beginner, or is that for if you're having mobility issues? I saw it comes with recipes. Have you tried them?

I started with beginner, but found it too easy so jumped to intermediate.  If you start a program then change it, if I remember right you lose any points you've gained.  You gain points for working out and consistency.  At certain levels you can get freebies, but you gotta get a lot of points.  The intermediate program is a mix of basic (Diamond Dozen 2.0), beginner (Energy 2.0, Fat Burner 2.0), intermediate (Red Hot Core 2.0, Below the Belt 2.0, Strength Builder 2.0, Stand Up 2.0) and advanced (Diamond Cutter 2.0) workouts.  You'll start with 3 workouts a week, and as you move along you'll start doing 6 or even 7 workouts a week by week 8, often two a day.  You can also substitute any workout on a given day if you don't want to do the one listed in the program or want to do one on a day off.  There are over 100 workout videos in the workout section from rebuild to extreme you can choose from.  So, long story short, unless you have some mobility issues, are rehabbing, or just totally out of shape, if you have any experience doing yoga and are in at least OK shape, you could probably start with the intermediate program.  After I'm done with this 13 week cycle, I'm gonna jump to the advanced program.
I have tried a couple of the recipes, I think a couple of omelettes awhile back.  They were pretty good and easy to make.  I just haven't been motivated enough to go buy the ingredients for some of the others , but I probably should.

A few of us get together during lunch at work and have done some of them.  Like everything else, anything will help you if you stick with it.