I am not sure that is what Bercow said on Marxh 18th. Here is the extract from Hansard:

Stephen Doughty (Cardiff South and Penarth) (Lab/Co-op)

On a point of order, Mr Speaker. Thank you for your statement today. The Government have gained an infamous historical reputation for trickery and abuse of Parliament during this whole process, and already rumours are going around that they might seek to use prorogation as a method of getting out of this. Can you confirm that that would not only provoke a greater constitutional crisis, but also result in us losing every single piece of legislation currently before both Houses, including many of the pieces of legislation needed to implement any Brexit?

Mr Speaker

If particular legislation was subject to carry-over, that would not apply, but in the expectation, let us say—or, to use a more neutral term, in the circumstance—that it was not subject to the carry-over procedure, manifestly and incontrovertibly it would fall. As for whether the Government are contemplating that, I have no way of knowing. No Minister has indicated that to me. I have no idea what is in their mind. It would be an unusual step, but look: I have been in this place a little over 20 years, and some quite unusual things have happened. I have no way of knowing whether this is being contemplated.