IIRC, it’s been used a couple times before with mostly the same results - in those cases, just minor to moderate wounds and no kills. Apparently even the ‘big’ JHP for the 5.7 doesn’t expand very well or reliably.
In the early sixties the government was experimenting with Personal Defense Weapon designs which used sawed off little .22 cartridges just like these. Erratic performance from short barrels was just one of the problems encountered. I was surprised when FN first marketed this series, to me it seemed a resurrection of a concept which failed 40 years earlier.