You're the one saying professional developers can't plan around a week off, you tell me.
In the grand scheme of things, a monthly update is insignificant when GT7 is one of the lead PS VR2 titles, launching on all new hardware in a matter of weeks. A huge technical undertaking that could quite literally transform the genre if it's implemented as well as we hope.
Before Christmas we where deciphering Kaz's Japanese interviews to garner the slightest bit of new info. Turns out, as expected, he was stringing journalists along, knowing a PS VR2 port was ready for the systems launch. Very likely in development since before GT7 itself launched. You can probably apply that to a PC port too.
The problem is people think PD are working month-to-month, when so many of these things are planned out months, if not years, in advance. There's no benefit for developers to spill the beans early, it just leads to disappointment if there are delays.