Piriform / CClearner team were unable to replicate the problem.
On Sep 6, 2018, I sent piriform videos of my phone, showing the LG v20 with android 8 (it also happened under 7), and the Maverick folder on the top level of internal memory, with all the data in it.
I then ran CCleaner, and it wiped out all that data in the Maverick folder. I am currently awaiting a response from piriform.