There may be laws prohibiting them from keeping information about employees/interns for that long. Many countries have information privacy laws (https://en.wikipedia.org/wiki/Information_privacy_law) stating that companies can only keep PII insofar as needed to operate their business, and keeping, for instance, your address around years after you left the company isn't needed to operate the business.
It typically is easier for a company to ditch an entire employee/intern record than to filter it for to-be-discarded information.
Of course, for employees or interns, they also typically are obliged to keep records for some time, for the tax office or because former employees might still file a claim.
Still, they probably will ditch everything they have on employees as soon as they are allowed to.
If they do that, they shouldn't say details about the employment in the email. You can get the same point across, that you want a candidate, without saying something potentially false.
The USA has weak laws there (https://en.wikipedia.org/wiki/Information_privacy_law#United...), but those of California are stronger, and the likes of Google run the risk of information 'leaking' to other countries.
It typically is easier for a company to ditch an entire employee/intern record than to filter it for to-be-discarded information.
Of course, for employees or interns, they also typically are obliged to keep records for some time, for the tax office or because former employees might still file a claim.
Still, they probably will ditch everything they have on employees as soon as they are allowed to.