Having the same problem but only in a very specific case. If I sysprep the image on the same machine that I deploy it to (for testing), it skips the rename. If I look in the setupact log file I find these lines:
Computer name in unattend [NAME HERE] matches the current current ComputerName [NAME HERE]
Skipping setting the same ComputerName
If I image any other machine it takes the pre-staged name fine. As far as I can tell it's a bug with 1803.