Google’s John Mueller states that when it comes to crawl budget, there is a possibility that Google might group your subdomains together for the purpose of crawl budget. John says “our systems try to figure out which infrastructure belongs together.”
There are assumptions that Google will have different crawl budget allocations per domain, subdomain, and on. But the reality is it depends upon the website, Google may or may not group all of your subdomains on the same domain for the crawl budget purposes.
Here Are The Tweets
It's possible we're already grouping the subdomains together for crawl budget — our systems try to figure out which infrastructure belongs together. I suspect you would see some crawling fluctuations there, but that settles down automatically as our systems figure it out.
— ? John ? (@JohnMu) March 31, 2021