I've fed on Aspen, I've fed on Repti Chip and I've fed on Reptile Prime.
The only problem I've ever had was one piece of Aspen and a piece of Repti Chip getting stuck in a mouth. They can usually work substrate out of their mouth, they do it in the wild. Even a bit swallowed poses no problem.
Its when it gets stuck, that creates a problem. Only happened twice in many years. I removed the pieces. The pieces were longer and thicker, sort of the shape of a big splinter. That is why I don't like chunky substrate or super fine (like coffee grounds) substrate. I really don't like splintery wood substrate.
If the substrate is soft and not chunky, if they ever do get some in their mouth, it won't be an issue. Most falls off while they work the rodent into their mouth.
I never place something on the substrate for them to eat off of. And the rodents are slightly wet. Still no problems.