Upgrading to SharePoint 2016, Missing WebPart Removal

Question

I'm trying to upgrade our on-prem SharePoint environment from 2013 to 2016. A goal of mine is to get rid of all the errors my predecessors had simply ignored during upgrades (from 2007, to 2010, to 2013) over the years.

Following this guide I managed to get rid of all the Missing Features and Missing SetupFile errors that is return when running Test-SPContentDatabase @testContentDBSplat, but I'm stuck on getting rid of the webparts. It's the same error list that's returned by Missing server side dependencies. in the Review Problems and Solutions page in Central Admin.

My issue is...

1. With the query he provides, the web parts that are referenced do not have an ID in the form g_bb56b03e_b830_4e37_ba16_62250601ac26. in the column AllWebParts.tp_WebPartTypeID It's typically just NULL

2. None of the web parts have been in the list supplied by $page.GetLimitedWebPartManager(...) as implied by his powershell script.

3. None of the other solutions I've looked at have come up with a solution other than "Look up the id [stated in part 1] and delete with PowerShell" or "Go to the page and delete the webpart by hand". I can't do the former, as the web parts aren't in any of the pages.

The Query I used to get the data to remove the web parts via powershell returns the following information:

And most scripts reference the value that should be in the last column, which is currently NULL

How can I get rid of these errors?