During the Q&A portion of a John Mueller Google hangout, John was asked about whether they roll out the same updates all the time, or if they stagger them.
John said that they don’t exactly hold back on updates during core update time.
The core updates themselves take about a week to roll out entirely. Even though a core update may be ongoing, this does not result in the “holding back” or delay of other updates.
There are usually lots of updates during this time.
Sometimes you might see Schema structured data updates. Other times, you might see shifting the UI by a couple of pixels or something. Maybe even a change in the colors that are being used.
Normal updates, however, are the types of updates where Google won’t hold anything back. They’re the kinds of updates that will keep rolling out one after another.
For updates like Schema, however, Google may hold back some of these types of updates, just so it doesn’t appear as if there is an avalanche of updates happening all at the same time.
The other regular updates that Google does are independent of the core updates.
This happens at approximately the 30:19 mark in the video.