Absolutely wouldn't surprise me, if they had no clue what data they have on individual users.
As soon as you have more than one team collecting user data (which they definitely have), you need to put in a dedicated effort to hook each team's database up to a centralized API for when a user requests their data or its deletion.
Such dedicated, centralized efforts don't mesh well with the capitalism-like system typically used at that scale of corporation. You'll especially have legacy or prototype projects for which no one is willing to invest the money to comply with laws.
Of course, this is not an excuse. This is Google's main source of income and they have had hard requirements for this since the GDPR took effect in 2018, and they knew about that coming since 2016.
If they still haven't bothered to comply with laws, they should absolutely be sued.