I assume you’ve seen this?
I’m sure that everybody is doing their best to get the beta out - but given that the book is only one of many of their responsibilities it may take a little more time to get out.
And as such I would expect the “print book” publishing date of 2018-06-10 to be tentative at this point (hence the phrasing “on or about”).
https://pragprog.com/book/phoenix14/programming-phoenix-1-4
This title will be available on or about 2018-06-10.