From the following quote from an SARC publication on grass carp it seems perhaps the short gut comment is relative to other herbivorious species, and not in comparison to omnivores or carnivores?

That said I can't see any other species having much longer intestines!

"The reason grass carp are so good at controlling aquatic vegetation is they
have a very short gut in comparison to othe herbivores. The short gut
decreases retention time (less than 8 hours) in the gut, and reduces
digestive effciency to only 60 or 70 percent, so they eat more vegetation."

http://govdocs.aquake.org/cgi/reprint/2003/729/7290120.pdf

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.