Unfortunately, the following link Tableau provides during the publishing process is more a tease than a real source of information.
Here's the link Learn how to reduce upload times
Someone interested in finding out how to reduce their content's upload times might think that following that link would get them to a place with some real, helpful information. Not so. They are instead taken here:
They'd be disappointed, possibly confused, and potentially lose some confidence in Tableau.
This page covers how to improve the interactive performance of your analyses, there's nothing here that appears to have any real connection to helping reduce upload times.
To be fair, "Extracting Large Text and Excel Files" is potentially somewhat related to reducing upload times inasmuch as extracting files may result in extracts that are smaller than the original source files and will therefore upload faster, but it's a reach to see how someone, particularly someone new to Tableau, would spot that connection.