SMART comes from the drive itself, and yes, it’s the only health data we really can read from an SSD. But that doesn’t automatically mean the numbers are always a perfect or complete reflection of the drive’s true condition.you are missing the point. of course the smart data is what the drive provides, but this is the point. when the drive reports too many bad sectors for an example it will report imminent failure. same for other errors. in the end the health endurance is pretty darn accurate for ssd health. to your point its the drive providing the info. so the smart data and endurance reflects the true health. smart data doesnt lie it provides the same info to all the apps you use they grab the raw data smart is providing. the drives also run self tests and report that as well.
SSDs can still fail without ever showing bad sectors, and different manufacturers interpret SMART attributes differently. Some attributes like “endurance” or “percentage used” are useful, but others are vendor specific or not standardized, so two drives can report similar issues very differently. And it’s also common for SSDs to die suddenly with clean SMART logs, it happens daily in the real world.
So SMART data is valuable and often points in the right direction, but it’s not infallible. It’s best treated as one indicator...helpful, but not the only thing to rely on, and unexpected failures can still happen even if SMART looks good.