I believe the newer Shockwaves are designed to cycle the short shells without an adapter.
They still make the original one that needs the adapter, but from Mossberg's site...
"For the ultimate in shooting flexibility, the all-new 590S Series cycles 1.75″, 2.75″, or 3″ shells."
https://www.mossberg.com/590s-shockwave-51601.html
But they are double what I paid several years ago. 🤑