As you know, Google told us the user agent names are changing in December, this month, with the new evergreen GoogleBot. Martin Splitt from Google said you may see this new user agent in your log files now, because Google is rolling it out as an experiment now before it is fully rolled out at some point this month.
Martin Splitt said on Twitter "The experiment is rolling out, but you might not see it immediately."
The experiment is rolling out, but you might not see it immediately :) //cc @rustybrick who asked a similar Q
— Martin Splitt @ 🇨🇭🏡 😴😴😴😴 (@g33konaut) December 16, 2019
So if you look closely, you might see it but it sounds like this is a small percentage of all crawling activity right now.
Forum discussion at Twitter.