I downloaded it portable version of CCleaner 5.75.8238 months ago to see if the ease of uninstalling Windows apps is available through it.
Because I had years to use it as an application that can only create problems (by deleting necessary logs and registry keys that it classifies as "junk") or that offers functions that you have at your disposal easily accessible (so what's the point?), I dealt out of curiosity and with the Options of the application.
In the selection Scheduling we see that it is disabled and available only in the pro version that you do not find portable on the official site.
In the selection Updates the first thing i did was turn off the available options. However, every time I ran it, the message appeared for newer versions, that is, it ignored the user's choice.
To Privacy I also turned off the options and that was the end of my work without getting into the process of re-using the application nor deleting the folder I had decompressed.
After some time from the above process, searching for the operating system I ran the Task Scheduler (taskschd.msc) and found two entries of the portable CCleaner to be active!
One is SkipUAC !!!! and the second CCleaner Update.
Nowhere do they mention that they will install scheduled tasks on your operating system:
While not even in the FAQ they mention anything
And search to be done with the word scheduler nowhere is there a report that the free home portable edition installs and without informing the user tasks that are even performed in each of his Login !!
Dozens of portable applications have been run on my system, from trial, free and none of them had such operating behavior.
Your own conclusions about piriform that unfortunately many pages insist on suggesting its applications for use.