Re-shaping right before oven?

you appear to have gotten away with it in this instance.  I would be very wary of reshaping before baking as you risk deflating the dough after all that time proofing.  In this case you had a boule so I assume all you did was tighten it up a little (?).  If so that might explain the success youi had as that wouldn't involve much disruption of most of the dough.  One might expect the loaf bottom to be fairly solid where the new seam was formed and I see that there is something of that nature in the picture just to the right of the niche at the bottom.  The level of hydration would greatly affect the effects of reshaping as you have done.  A wetter dough would likely collapse if handled esp something like baguettes.

It's more important I think for you to concentrate on the root cause of the lack of oven spring you have been experiencing.  It could be a number of things including over proofing, poor initial shaping, low oven temp, lack of steam etc.   Could you provide a little more info on how you are loading the bread into the oven?  Recipe might also help and your basic proofing process.  I'm sure you'll get some good suggestions from the forumites here.

Yes I have tried this.  Recently I let a pumpernickel rise too long.  It is so difficult to handle.  So I just tipped it out of the loaf pan, did a quick one-handed roll to reshape it, and baked it.  It came out fine.  Another time we kept missing the timing on the steam (my cheap oven gives us steam, but not 'on demand').  I think three times that raisin cinnamon loaf rose and was punched back before baking.  I thought it would be ruined, but the only effect was larger holes in the crumb.  Yeast is amazing stuff!  It keeps coming back.