Yes, it's true. If you haven't cleaned them, your tubes are holding stagnant water. Mold loves that sorta shit. You 'can' rid yourself of mold with a bleach solution, however, enema tubes are cheap enough that they are virtually disposable and not worth the effort of cleaning and perhaps missing some spots. Do yourself a favor and just buy new tubing.
Greeting, While they can be cleaned it is far safer to just buy extra tubing. There are many things that like to grow in them besides mold which can be harmful. Respectfully,