Doesn't that link show that the how backups related to GDPR is still up for debate? The accepted answer that says they are included has 3 upvotes and there is an answer that says no they aren't included that has 2 upvotes. Either way, the legal requirement is a separate issue from what Instagram is actually doing. If that download tool is automated, I am rather confident in saying that it isn't combing through year old backups to get data.

Ever wonder why "download my data" usually takes a few hours/days on most services before you receive the download link in your email? I promise you compiling the production data doesn't take that long.

Backups are covered under GDPR, although when a user requests erasure you can say "your data will be rotated out in X months/years". Not sure how this applies to access, but I assume it's similar: https://ico.org.uk/for-organisations/guide-to-data-protectio...