Often it's not the case, which is why general consensus with SSD's for ZFS SLOG devices is to go with ones that advertise end-to-end power loss protection unless sufficient testing has been done to guarantee the drive protects against partial-writes and doesn't lie about a flush being complete.
Samsung has bigger issues with writes though, almost all of their current drives are TLC NAND which has extremely poor write performance so while short bursty writes can be fast (due to there being a chunk of SLC NAND cells as a write buffer) sustained writes are terribly slow. Optane doesn't typically meet the same peak write performance but it will beat most (all?) TLC drives on the market in sustained workloads.
The sustained write performance is why you might buy a Samsung PRO model. The PRO models have a lower burst write but can sustain high write speeds indefinitely, while the EVO model's speed crashes when it hits the limit.
