The certificate transparency log lets everyone know which domains are active as the certificates are getting renewed, likely more often than the domain itself, and also which sub-domains are active if those are not secured using a wild-card certificate.
Not just Google: AI bots could use the information to look for juicy new data to scrape and ingest.
Probably not a significant thing, the information can be derived in other ways too if someone wants to track these things, but it is a thing.
This doesn't feel like much of an argument in favor of not using https though.
Not at all IMO, unless you are really paranoid about Google & friends. I was just saying that what was being questioned does (or could) benefit them a tiny bit.