Those digger sheaths look like a possible pita for the digger blades needing to constantly be cleaned every time it's being reinserted in the sheath following any kind of soggy dirt digs. My diggers simply dangle off my belt. I mainly dig with a Mini-18". That sheath looks like a pain to me since it is so snug and it has no open-exit for the dirt to easily drop out.
All in all, I foresee lost time messing with closed sheaths for diggers.
Jm2c.