I don’t think it’s worth it. I’ve tested the SPECIAL fairly thoroughly, if artificially, and saw little or no real benefit in practice, even when trying to do things like run a find against tens of thousands of files (which means lots and lots of metadata).
This was on a system with eight 12TB Ironwolf in mirrors. Basically, four mirror vdevs of those drives just had enough oomph to handle most any artificial benchmark I threw at them–and the benchmarks that they struggled with, they struggled as or nearly as hard with or without the SPECIAL.
I think the most likely benefit you’d see would be the possibly less platter-chatter than you’re accustomed to, but can’t actually promise that either.
Honestly, if you’ve got a pair of fast SSDs burning a hole in your pocket I’d say spin up a separate, blazing-fast pool for any separate, blazing-fast storage needs you might have. You’ll get better use out of them that way.