HDDs and SSDs age very differently.
HDD's are 'just' monitoring various attributes like spin up time, temps, various counts, damaged sectors etc. If these are all normal then it's 100%, but it could fail tomorrow, with no further warning. They are just indicators that we know when they go bad the drive is likely to have a problem.
SSD's monitor some of these same things, but also they are known to have a limited number of write cycles per flash cell, depending on the architecture 1,500-10,000 (10,000 is impossible to buy now). The controller takes account of how much spare capacity it has to replace worn out cells, how much writing has occurred, and it knows that it has used up n% of it's rated ability to write data. This is what is likely to be the cause of your reduced percentage.
Reading the HDD 79% i'd be worried, it'll mean lots of bad sectors and something that it deteriorating.
Reading the same 79% on an SSD i'd not be at all worried as it's just telling me that you can use it for 5x longer than you already have before it runs out of the ability to write. Assuming this is solely a write problem i'd be happy taking it down to 10%, or as a storage drive 5%, with a HDD i'd be swapping it at 90% ish.
Given it is solid state this is the only 'wear' that occurs, and it is predictable and the drives are built to manage it, for HDD's it's not very predictable and nothing can be done to manage it.