My Windows 10 setup, made to look like Win XP.

It doesn't, and a generic filter in Windhawk has caused issues for me in the past. As an alternative solution, you can of course have an observer program that looks for all SysListView32 elements and clears their style. The general pattern to set classic theme on a window (particularly a child window with uxtheme otherwise used) is as follows:

But my solution in this script was to hook OpenThemeData. If I had to guess, having slightly more experience with hooking internal functions like this now, it is possible for an invalid pointer string pointer to be given to the function via pszClassList, which means that you can't necessarily trust dereferencing it. You can workaround 99% of crashes with a check using IsBadStringPtr, no matter how much people say this is a bad function to use or whatever. So then, I assume the crash I was receiving previously was caused by an access violation by string functions expecting a null terminator that doesn't quite exist (they read memory starting from that pointer until the next 0x0000 string for wide characters). So I might experiment again with such an implementation implementing this correction.

Furthermore, I suppose that could extend support to the DirectUI view that File Explorer itself uses, although I am not sure. The above classic theme method does not work for the DirectUI view, but OpenThemeData might, since DUI uses uxtheme it most definitely calls it, but probably doesn't take from the window theme of the host window.