FWIW: I've had a river knife strapped to my PFD for 25 years, on hundreds of full-sized raft trips mostly Class III, some IV and V, and a half-dozen or so serious on-river incidents.
Never ever used it.
And I'll always take it.
Barely visible in my avatar, right side of photo, above blue carabiners. I recently replaced that PFD, but kept the knife.
For packrafting, I'd take the lightest knife with at least a 2 inch blade, that I could strap to my body/PFD, and that I could remove quickly and use with one hand while being thrashed underwater. No folding knife would meet those criteria.
The good news is you could leave other knife-like objects home on those trips.
Solo vs group packrafting would not matter, a knife could save you or your buddies from deadly adventures with ropes, fishing lines, small branches, or pinned boats.