I have no clue why they didn't just move it all the way up after Moscow since it was obvious it was too much that late in the set. Maybe there was some hesitation in the band about making a pretty huge change to the flow of the set like that? Who knows. Could've also been the crew since maybe setting up Janick's acoustic right after 2MTM was considered a bit of a hassle.
Maybe they also wanted to give the set, in the form it was then anyway, another go without the usual "rust of the first gig." Sometimes the first night of the tour is considerably rusty and tough, especially for Bruce, and they might have thought it would eventually settle very well as the tour rolled onwards. Seventh Son was a bit rough delivery by Bruce at the first night of the 2012 in Charlotte, but got considerably better very soon.
I agree it's a bit strange though and given their experience, one might assume this issue would've been tackled in the rehearsals. I think they've often mentioned that they do a couple of run-throughs of the whole set before they'll take it to the road and usually that kind of things surface and get fixed there before the first gig.