If I search for content, and results return documents that have not previously had thumbnails generated, the tumbnail is generated but the document is shown as modified based on that action. This resulted- today- based on a seach I did of me being shown as modifying a range of content 'a few moments' ago- which is confusing. But more than that, modified date/owner is an indicator of how up-to-date content is. This behaviour makes that much less useful as it is not a date of when the content was modified. There should be a separate date for when some activity updated content metadata & thumbs, and a separate item that tracks when the content itself changes.