Did you drop your front ring size when you put the bigger wheels on? Even if you you did, I imagine a slight change in the precise ratio to the dirt could affect climbing traction, especially when in a very familiar situation where 'muscle memory' has a significant contribution. Not suggesting it isn't inertia necessarily, I think that's a totally viable explanation. Just providing an alternative to ponder.
Also, did your suspension settings change? Impossible to say on the fork I guess, but the shock. In theory when riding at a given speed, suspension shaft speeds should be slower when increasing wheel size. Just wondering whether that was enough to warrant a click of compression damping to you. Do you know if the suspension manufacturers account for this in their tune of forks for different size wheels? I'm guessing no, and that I'm just a massive nerd.