Except you could have simmed similar examples all xpac, as I did when people stressed this so much. See the problem is people are stuck in the mindset and never bothered to even give it thought. Myself and traherne back and forthed on stacking haste(and specific breakpoints) vs mastery for the last two tiers and tried everything in between and never once found any tangible difference in dps in raid with us doing drastically different reforges over and over.
While I agree simcraft is freaking terrible I know you know no other logs or anything I could show you are going to be anything more than anecdotal at best considering how insanely different a single pulls dps can be. In any gear stacking mastery > haste ignoring breakpoints always lands you with a healthy amount of haste. Even in my own gear right now which is far from Aff BiS I end up with 12.9k haste proiritizing mastery completely. I see no tangible difference in dps going from 12.9 to the 13.2k breakpoint, Further I see no tangible difference going from the 13.2k breakpoint to the 13.7k breakpoint.
I've simmed and theoried and live tested arbitrary amounts of prioritizing haste over mastery, mastery over haste, and very specific breakpoints to death and never once found any tangible difference between them outside of pure preference as long as your gear wasn't super fucked up with massive amounts of crit.
What *proof* would you consider legitimate proof? You know any logs I provide would be anecdotal and I could throw more crappy simcrafts at you for random various breakpoints and it would end up showing the same thing (as it has been doing the whole expac) and it would still be simcraft. I mean shit dude pet dps has been normalized since the start of the xpac and yet people still INSIST observer is by far the highest dps pet because they never bother to check any better. Just because people get stuck in mindsets for an entire xpac doesn't mean they're right and if what they're doing doesn't have a tangible difference otherwise (for instance switching a pet or not caring about a breakpoint) they'll never bother to thoroughly test it and just keep on being *convinced* of its "truth".