Yea, bud, I was just looking at your swing from June on your swing thread, and that left arm doesn't come down fast enough. I dunno if that's a priority for you or whatever, but yea, that'd be why your left shoulder is rising excessively.
You can see how much farther downward the left arm has traveled in Mike on the right compared to you on the left.
And I know you're not hitting a golf ball and that this swing I'm using was from back in June, but the reason I wonder as to which is the priority piece is because of how the lower body is working here. The right foot is well up onto its toe and the right knee just kicks out and is flexed a lot.
You'd probably benefit greatly from this new video here from Erik and Dave:
The right foot banks onto its instep before it releases upwards like you do onto the toes, and the right knee definitely doesn't stay that flexed either. Very common problem. Frankly, both topics here are. There are a bunch of other drills out there to fix the second problem, but the above 5SK video is just one way. And you know, I think this lower body action you make stems from just not enough hip slide (could be wrong).
Per your initial question, you can see how in the Mike example on the left how much higher the lead shoulder gets vs. the example on the right, when the left arm comes down at the correct rate.
PS- Sorry, I know this isn't your swing thread.