Facebook collected data for ages using their SDK and lists of e-mail addresses/phone numbers submitted to them by advertisers but only started exposing them in their "download my data" tool (their GDPR SAR process basically) relatively recently.
GDPR access requests don't always tell the truth, often due to malice but in some cases incompetence too (there were a couple of times where my GDPR complaints have actually revealed to the company that their third-party SDKs leaked more data than they originally thought).
Facebook collected data for ages using their SDK and lists of e-mail addresses/phone numbers submitted to them by advertisers but only started exposing them in their "download my data" tool (their GDPR SAR process basically) relatively recently.
GDPR access requests don't always tell the truth, often due to malice but in some cases incompetence too (there were a couple of times where my GDPR complaints have actually revealed to the company that their third-party SDKs leaked more data than they originally thought).