That's not shock or stress. It is genetic diversity.
You can flip to flower anytime you want.. whether no or when you fill in more scorg it is 100% up to you and you can make it work either way.
If you wait for the other one to spread out more, you may need to prune the other one back a bit... whatever it takes to even it out. I'd expect the one on the left to continue to outpace the one on the right. You can mitigate this by continuing to train the one on the left beyond flip to flower... maybe 3-5 days longer? a week? depends on the difference in vertical growth you are seeing so far (or horizontal growth in this case as you train it to the scrog, lol, not the axial growth)
Usually when you fill about 1/2 the sapce, it's good to flip. Obvioulsy 1 plant is getting there sooner. Allowing one to cover more ground can help, but once they are tangled in teh scrog, you can't really move them around much, so there is some limitation in that.
Try to train the smaller away from the larger plant and let the larger plant encroach on the smaller plant etc... Train the larger plant beyond flip while allowing the smaller plant to start growing vertically to offset inevitable height difference.
This is more art than science because you have no idea how each will grow after flip, but usually they don't change their spots drastically.
If the smaller one isn't in the net, could get a pot elevator/riser to raise it up. If not tangled in scrog, i'd shift it away from the bigger plant so the bigger plant can use up a larger portion of the space than 1/2.
any way you can slow one down and allow the other to start growing vertically earlier will help keep the canopy level later on. Anything you can do to reposition and or train the plants to better fill the area will have a positive effect on your yield.
The only way you avoid this is using clones of the same plant. PAy attention, because you'll be doing this again and the more comfortable you are the better. You understand the basics of apical dominance / training, now manipulate the plants for best results. Nothing you can do about genetic diversity but try to mitigate the differences as best you can.