...source Janzen's Notebook pg. 83 - Model 1898 a/A - shortened - "...units shortened these bayonets on their own authority for trench knives."
The plot thickens!
I think it makes all the sense in the world to grind it down for use as a trench fighting knife, desperate times call for desperate measures, I guess.
The psychological impact of a charging mass of troops with the full length bayonets must have been something else, but using what must have felt like a sword one on one at bad breath distance?...not so much.
Great info and replies, all! Thanks for filling in the gaps here.