I don’t know the true reason, but a few logical ones I can think...

I don’t know the true reason, but a few logical ones I can think of are:

1. The update, if released today, isn’t going to be great, but there’s a possibility (however small) that a deal could be closed imminently, so they’re delaying as long as possible to give one of them a chance to close. 

2. There are some difficult, unresolved, items they have not managed to agree yet on suitability of wording.

3. They don’t think it’s important to be concurrent (remember the last one was released about a week after the 4c). 

There are probably many other logical reasons, but a deliberate desire to frustrate shareholders is not one of them.