Consistency is key for flexibility training so maybe if you stick to it you'll see better results ;-) What I usually do is to stretch after my pole training, cycling between front splits, middle splits, back, etc. I'm usually too lazy to schedule a flexibility session alone, not to mention going to flexibility class. After your pole session you are already warmed up so your flex session can be shorter and more efficient as you don't need to fully warm up, maybe just some areas where you want to focus more.
Regarding square vs. open: I've just learnt that an open split is not a poorly executed split. It's a different exercise that requires different muscle elongation. Open splits require more inner thigh flexibility and less hip flexor flexibility. For some people, square splits may be easier than open splits. Not me but tough!!! I have my open front split and I'm very close to my middle... My back flexibility is lackluster so there you have it, tight hip flexors. I think it also has to do with your body composition, hips structure, etc.
Good luck!!
