Sarlac that lost the ability to grow 'roots' and instead worked out venom and energy storage (fat and muscle) would outcompete and supplant the sarlacs still producing energetically-expensive, overly-complicated stasis bellies.

What happens if they momentarily fail to keep their meals alive, do they starve or become poisoned by the rotting meat? Do they have issues keeping a varied diet alive? How do they maintain a net positive energy balance after producing all that is required to keep organisms alive? Why not stun them and stash them, like wasps and spiders? Why not fatten up like -gestures broadly at all life-. Fat requires very little maintenance.

Could one, in theory, rescue one's friends were they trapped in a sarlac?

Sounds like an organism that would quickly be out of business were there any competition at all.

edit: How do they handle the waste produced by the meals-in-stasis?