That is a good question. It maybe that any potential buyer has a check list of items to go over and having a PEA is one of them. If this was a gold find, I think that Zen would be bought up in a heart beat. However, with graphite and its many applications its science that is going to help sell the deposit. And that takes time.
Try to put yourself in the position of a company that is looking to aquire a deposit and you are responsible for buying. You want to make sure that all bases are covered.
I think that any company looking to buy must perform its own DD, at its own pace. And that pace is never as fast as those that want to be bought out.
Anyway, its all good.