This is interesting, and I can see the potential merit of it. There are some unknowns here, at least to me, that perhaps some of you could clear up for me.
Say CCleaner writes whatever to the free space of a drive, in this case a SSD. Is that one or more large files, that are then "deleted", by sending a delete request to the OS? If so, then I see how it works on a SSD. The deleted files cause TRIM commands to be sent to the SSD, which will cause some major GC to occur.
That is similar to the "forced TRIM" programs that are seen now and then. They write to the SSD, and then delete what was written. The SSD controller may even find some bad blocks during that process, and mark them as unusable, and use blocks in the spare area as replacements. That might also explain why the OP's SSD was fixed by this procedure.
Yes, this uses up a program/erase cycle on all the affected bits, but I agree that the concern about conserving P/E cycles is blown way out of proportion. The notion of being a slave to a SSD means we would do everything possible to save the precious PE cycles. I was like that initially with my first SSDs, but have abandon that, I just use them as they were meant to be used. Considering all the worthless logging that Windows does, like "The boot time did not degrade...", using P/E cycles to clean up a SSD are P/E cycles well spent.
It dont wipe free space,it loads free space. Of course it does, it was meant for use with HDDs, where the term "wiping" means making whatever was on the HDD unreadable. On HDDs, that is done by writing over the data currently there. On a HDD, the "free space" can contain deleted files that have not been overwritten yet, so have the potential to be retrieved. Of course there is no reason to "wipe" a SSD the vast majority of the time, but occasionally it can be worthwhile.
A question to ponder, does a Secure Erase use P/E cycles?