I wasn't doing this forever and my left hip flexor got all fucked up. I thought I was, but then I did it, and realized I wasn't. Some week external rotators might have been to blame and I spent a lot of time on the good/girl bad girl machine and doing bird dogs.
This was ridiculously tight on my left side:
A couple other stretches and some foam rolling got it evened out. It probably would have went away on its own if I fixed my squat form sooner.