A screenshot records what a screen displayed, including its scaling and possible interface elements. A direct image download usually gives you a cleaner starting point for inspecting an available thumbnail.
Compare the contents
Check whether the screenshot includes browser controls, borders, or overlays. It may also capture an image after it has been resized to fit your screen. The downloaded file preserves the particular image variant you selected rather than the surrounding page.
Use the appropriate record
For artwork reference, save the available image. For documenting how a page looked at a specific moment, a screenshot may be useful because the interface is part of the evidence. Label these purposes separately.
Avoid accidental substitution
Do not place a screenshot into your design archive as though it were the original thumbnail export. Keep its source context and capture date. When detail matters, compare the screenshot with the direct file and use the best legitimate source available for the task.