I am sure that there are different species of each type of snails so not saying that all of them within any group do this...but some Trumpet snails do not limit their eating to dead plant matter. I had a tank full of vals which trumpet snails killed by eating off the roots thereof. They also have aten through the stems of Java moss as it seems they like the algae that sometimes gets on there but fail to stop eating when they reach the bottom of the algae. I seem to see/find many small pieces of the Java Fern cut from the main part and laying on the bottom of the tank only when I have trumpet snails in a tank. I am just assuming that is where those small pieces came from.
FWIW....I have never heard this about Malaysian Trumpet snails.
The ones which did this were "collected" from natural sources in southern Louisiana and in Arkansaw where I now live.
But I appreciate your thread as many do panic over something which, for example might keep the algae off of the leaves of an Anubias plant.
The shortest distance between any two points is a straight line...in the opposite direction...