That's the promise. In practice your SSD might kill itself due to a bug in the firmware and drop off the bus without warning long before the flash is worn out.
I can't even remember reading any reports of read only failure due to flash exhaustion. I do remember boat loads of early SSDs, mostly sandforce based ones, spontaneously dying due to firmware bugs.
Electronic parts can fail silently and without warning in either case, e.g. due to a tin whisker producing a short somewhere.
Mechanical parts being less reliable than electronic parts in HDDs, and their relatively slow degradation, allow for an earlier warning when data can still be recovered but the drive should rather be replaced.
