G’day Tom, here at Buderim, near the coast, we also get low viscosity honey this time of year. I always make sure the cells are fully capped, (as you did) before harvesting the honey.
It’s not so much capillary action that causes wet caps to separate, causing a leak, I believe it’s the surface tension of the cap on the honey that causes the cap to move with the honey, once the honey starts to flow. Very similar to a leaf floating on water, that moves as the water moves.
I not long came home with some honey to extract today. This is 5 frames out of the 8 boxes I intend on extracting. I chose these photos because you’ll see wet caps, dry caps, a wet & dry combination, as well as sunken caps (concaved) & nicely convexed caps. I love them all to be convexed, it makes de-capping a dream. The bees don’t see it my way 
It’ll still be a dream run because the majority of the cappings are convexed.
cheers