Which is why I said from the beginning "Arm Bar" is a no teach. Hitter going to do what's necessary to barrel up the ball. I've seen some ridiculous bent elbow swings to get to an inside pitch as well.. not an idea swing, but necessary and efficient in that situation. Arm bar is bad when the lead arm gets pinned to the hitters body because the hands are left behind and the hitters trunk has already started to rotate.. that needs to be corrected. Arm bar can be just has efficient as any bent elbow swing depending on pitch location.. and who's swinging the bat. I see many more LH handed hitters(right hand dominated) bar their lead arm.
Now it sounds like you are preaching to the choir. As I have said over and over, it is a reaction to specific pitches, and their dynamics, as in reaching to "barrel" the ball, or getting fooled. But to teach a barred-arm as basic, fundamental is foolish, because you are teaching a longer swing of totally rotational nature. I don't believe in a pure rotational swing. I don't believe in a pure 100% linear swing! I believe in about 50/50. Athletes do what they need to do in a quest for success.
I agree about the lead arm. But my indicator of a good swing is, were they able to achieve full extension? And was that full extension where they hit the ball. I din't mean a sweeping arm-bar full extension, but a linear, directed full extension. If not, the swing was compromised, and maybe necessarily so. Below Rica has a purely rotational and compromised swing (did have!). Aaron Judge is even more compromised. I also had a Mike Trout swing up and in, the same. Were they even strikes?