Hey that's legit form, just know that flat footed tends to hit quads/hams/glutes pretty much equally, and shifting more onto the balls emphasizes the quads. Squatting solely on the balls of your feet tends to lead to underdeveloped glutes and hams overtime. I actually do sets in both forms to get a good mix.
I guess I do that too, but accidently, LOL
About your pics, WOW you are clearly showing more cuts in the latest shots. Good job!