The lead to the article says "You might be changing an email provider, or you require a copy of your data for safekeeping" but only provides an explanation of the second reason (data for safekeeping). The first reason (changing to an email provider) is more important, given Google's recent decision to force "free" family accounts to be paid business accounts. Please could you update the article and provide details of this process. Can other email providers just import MBOX files? Or multiple MBOX files?
Another good reason to backup your Gmail regularly is that Google might block and ban your account for any stupid reason they come out with, and unless you are an influencer on the web, you can forget the possibility to unban your account.