SSD, if the manufacturer were honest, would include wear level data and all the necessary information for this application to do its work.
Do you seriously believe a 7-8 years old HDD can still be 100% healthy like a brand new drive? I have had an HDD which had a board failure after 6 years, and these type of apps wouldn't warn you (how can it, it just doesn't have the info).
You cannot depend on it for an HDD because if an HDD does not have a bad sector, the application will not lower its rating on the drive, even if the drive had been used for years.
No, like all these apps, those values are indicative only.