Nigel quotes the following:

From your link: "John Bercow, the Speaker of the House of Commons, has set the government a deadline of Tuesday evening to publish the Brexit assessments demanded by parliament or explain why it has not done so.


I don't know what the link referred to said, but you can look in Hansard for what the Speaker said. The bit in bold is truncated: Bercow said "...Failing that, I expect Ministers to explain to the House before we rise tomorrow evening why they have not provided them and when they propose to do so."

So the papers must be published on his instruction. All the Government can explain is why they have not been released immediately.