how did he disable the VCM before your test drive ??
Just wanted to post a follow-up.
The service manager was able to replicate my issue after I took him for a drive. He went back out with the diag laptop, captured data, and sent it to Honda's tech line. Tech line insists that what we're feeling is VCM engagement and there is no trans slippage. They're insisting that the vehicle is operating as expected. Manager was skeptical so he took an Odyssey out and validated that it does the same thing once warm, so he also disabled VCM on my Ridgeline and took it for another drive. The behavior disappeared. Whoever at Honda decided that a five-second rumble and tach bounce on the highway constituted an acceptable VCM experience needs to have their head examined, every other manufacturer I've used with variable cylinder tech has done it in a far more transparent manner (even Dodge, and they're awful).
Solid service experience with Honda of Grand Blanc MI, and I am very pleased with the effort and constant communication demonstrated by the service staff. This one is wholly a corporate problem, nothing wrong with the dealership at all.
Time to invest in a muzzler, I guess.