Traincraft hasn't had a mod spotlight by Dire so that could be the reason for that one and PetroGen is a niche mod to fill a gap in energy conversion while Dire prefers to make a specific power system for each build. Dire never used Rei's in his SSP LP, Twilight Forest isn't his sort of LP style but is a nice addition to the mod pack list, Gregtech is annoying from a purely LP standpoint so is probably out for that reason, Extra Bees based on the feedback from viewers would just not be worth the effort and Voxel is purely a visual and would rarely get seen in his LP.
On the other side of things, looking at what is missing, most of it isn't that surprising. Everything else matches to what you said though. Gravisuite actually is on the list for Dire's and the mod in the folder is called 'mod_zGraviSuite_1_6'. Compact/Advanced Solars are independant but share the same purpose. With Mystcraft I expect it will be added but the mod was updated pretty late on from what I can tell so they probably didn't add it to the Mindcrack pack yet (and the word on Myst was that it adds no world generation so is easily added later).
WRCBE is the same thing as Wireless Redstone - CBE so nothing to mention there.
