What i found interesting also was the time delay between Nintendo internal tests on these final dev kits (which happened at the very least in the first-half of February, maybe earlier), and their arrival in May.
And third-parties were warned by Nintendo since late february/march (so not long after these internal benchmarks) that they will receive them soon (before april).
So there has been a postponing of 1 month+, and it doesn't seems it was because of shipping problems from what i know. It could be more time spent for their assembly, but it shouldn't explain 5 or 6 weeks of lateness. It really looks like Nintendo have been keeping their tweaking/tests/changes on these dev kits for longer that they expected and that they noticed foreign studios. Maybe some late arrival of a finalized component also ?
This is a rather positive news about the hardware performances imo, considering the V4 dev kits were already quite competent (a question of perspective of course, read my other entries in thread 3 or 4 to know it).
TLDR: It seems Nintendo tweaked (& built + shipped) those final dev kits from at least late january/february to late april/may, and for 5 weeks more than what they planned. It's promising about their power (nothing huge though) and above all what they include, their features, etc.