if you try to upload the same exact video youtube will stop and block it. It would be bad if people just kept uploading the same video.
in general Youtube doesn't compare content ID on your own videos against your own videos
instead, I assume they are performing a check sum equation to see if the video clips are the same exact clip
in a checksum, even changing a single bit would change the end number completely
if you just re render the video, youtube will see it as a new video because on the bits and bytes level it's different enough
So in the same way changing the video length, even by a single frame changes the save file and will have a completely different checksum (sort of like an ID number)
and like I mentioned before even re rendering the video will change the file and will pass this checksum test
I know because i've had to reupload videos that failed to upload and my reupload gets flagged as a duplicate until i re render the video
Image of checksum for text files -
View attachment 45066