In this climate of heightened, even ridiculous, security compliance expectations (like the GDPR), businesses and their IT staff have mandates from multiple sources to reliably remove specific data content, on request, from every source.
When this requirement falls to SharePoint site stored data, like from Microsoft Teams Projects, you run into the problem of ‘revisioned’ files still containing the data, after removing the content from the existing branch. In other words, the prior versions of the files contain the data needing to be removed, after the Master branch content is deleted. I have been searching, but don’t yet see, a clear resolution provided by Microsoft to answer this security mandate, short of deleting all versions of the entire file, which is not a real solution. Just saying, “This data is owned solely by the customer.” doesn’t answer this specific problem, Microsoft.