in review… the digestion of a long chain of glucose, (like starch or cellulose) our enzymes are acting on the polymer chain…the ultimate goal is to get the energy from each one of the glucoses through fermentation (namely, glycolysis). If you ingest simple glucose, rather than a chain of glucoses you bypass the enzyme process to break the chain.
Alternatively, energy can be achieved by oxidative phosphorylation. Involves exchanging phosphate groups and oxygen. Reactions are influenced by pH, ions, and transport availability, membrane potential, gradients, etc. significant for the sodim-potassium pump (ATP processing).
Fiber can help present molecules for a longer period of time based on rheology. And polymers such as thickeners (cellulose chains of glucose) can alter rheology: If its thicker, the idea being the molecules are available to be processed for a longer period of time. Any nutrients then as well.
For the specific chain, cellulose versus psyllium versus starch for that matter, check your product, as even prodiem has both products (cellulose or psyllium). if there is a problem, it would seem to me you are suggesting the individual molecule of the chain is contributing. The approach though to use a thickener to slow the system to get and benefit from the energy and nutrients.
Now as far as experience, I noticed that a carboxymethylcellulose based ice cream (soft serve for example) may be better tolerated than regular ice cream (all lactose, milk, and glucose problems aside for a second). Suggesting an emulsion benefits processing. You can make your own emulsion simply by mixing starch (boiled potatoes) in a blender and adding other nutrients. As opposed to purchasing metamucil which I always felt bloated.
The bottom line however is that somewhere the good bacteria and the glycolysis has gone awry. Or something within oxidative phosphorylation.