One other note about SLOGs. They are basically write only devices, EXCEPT during a crash / power failure that had outstanding writes still on SLOG but not in pool. Then, they are useful.
And to be crystal clear, ZFS was was specifically designed with crashes / power failures in mind. Pool corruption is not going to happen unless their is other hardware at fault. (Like disk failure.) Data blocks are written as "copy on write", so the prior data / metadata, (aka directory info), remains intact, even after the very top level pointers are changed to the new data. (Of course, after that, the old data is then free to be over-written.)
In the even of a crash or power failure, any data in flight is either going to be stored correctly, or lost. And any file system can loose data in flight.