When you capture query metrics through trace events or extended events, either using rpc_completed or sql_batch_completed, you not only get the query. You also get any parameter values associated with that query. Article 17 of the GDPR is extremely clear:
The data subject shall have the right to obtain from the controller the erasure of personal data concerning him or her without undue delay and the controller shall have the obligation to erase personal data without undue delay…
While there are a list of exceptions to the definitions of Article 17 listed at the link, none of those is because the data isn’t in the database or is stored in some separate information store such as your monitoring of queries. Instead, the GDPR pretty much says that any place (SharePoint, Excel, etc.) that the data resides, must be documented as part of your processing and is subject to control through the Regulation.
Read the whole thing.