Cali, I`m still trying to find a reasonable answer to your Wisteria phenomenon and have been doing some research on the internet.
The time from flower bud initiation (FBI) to flowering varies for each plant species. For example Arabis (bittercress), probably the most researched plant species, takes about 13 days while Annona, custard apple, takes 33days. A Japanese reference said that FBI to flowering for Wisteria takes between half and one month.
Therefore, and this is a big jump, if Wisteria flowering usually occurs about April 1st (to keep it easy) we can assume that the FBI was made early to mid March.
For arguments sake, let`s say that LBI (leaf) takes the same time but some two weeks later then we can plot a time-line for your situation.
Thus FBI commenced early to mid March and proceeded normally until the warm period at the end of March/April with flowers emerging on April 14th. However LBI started two weeks later on April1st in the middle of the warm spell with emergence on April 14th, the same time as the flowers.
I wonder??? Hope it makes sense.