Suppose you have an opening title made in AE. Something more complicated than a MOGRT. You cut it into several timelines in Pr. Now you need to adjust the AE comp. If you Edit Original and it takes you back to AE, you can overwrite the existing file, and it will update all the timelines in Pr.
However, if you go to AE directly (without using Edit Original, or there is no link) and overwrite the file, the video will be corrupted in PR. Typically, it will be blank for some or all of the clip, and Pr will report a frame recursion error.
I understand that overwriting the file without the link being used might break the link, but why corrupt the file? If Pr is closed during the render, everything will be fine and updated when it's reopened.