TBH I got Fences 3 in 2017 and I haven't had a version yet that doesn't have SOME bugs, so I'm a little nervous about gambling my currently working install to help y'all with diagnostics by installing a version I can't afford to buy right now... But I can test it in Windows Sandbox at least!
Fences 3.13: Fired up the Sandbox, grabbed the 3.13 installer that was found, installed it as a trial. Using the Show Desktop button on the taskbar in the Sandbox does not trigger the high CPU issue.
Fences 3.16: I logged in to my Stardock account to get the current Fences 3.16 installer, but installed it as a trial. Using the Show Desktop button on the taskbar in the Sandbox does trigger the Windows Explorer high CPU issue. Disabling Fences 3.16 fixes the issue, re-enabling it and pressing Show Desktop again re-triggers it, as expected.
Fences 5: I restarted the Sandbox to get a fresh one, grabbed the Fences 5 installer, installed it as a trial, and pressed the Show Desktop button on the taskbar in the Sandbox. Fences 5 did not trigger the high CPU issue.
The changelog for 3.16 just lists "Miscellaneous installer changes". Were there any changes to the program itself, or was it just the new pop-up advertising Fences 5 that got added? The pop-up shows up for the 3.16 trial, but not the 3.13 trial. I'm hoping this is a Hanlon's razor moment, but ngl, the first update in nearly 3 years not having any patch notes, breaking the old version, and not having an official way to restore functionality is kinda sus