This makes no sense. It's not a "razor blade." It's a model (or other) maker's Olfa snap-off blade. It means they were either the maker or they went specifically to a store and bought the most expensive option for a craftsman's blade replacement available, disassembled the seat and inserted the blade, which looks to still have about 2" of blade left. These blades are often difficult to locate for purchase and I used to get them only at niche supply stores.
What seems more likely is this piece of shit saddle was made in some terrible factory and it got lost in the production process. Notice the clear plastic exposing the cheap foam below. Who does this with a saddle? It's low-grade vinyl, plastic and foam. I bet there isn't any gel at all under there either.
It is a common thing to find all kinds of junk coming from low quality overseas manufacturers. We have to contend with this headache all the time. The only way to ensure even the most low-end quality control is to have a guy stationed there, watching everything like a hawk all day every day. This is physically impossible when dealing with mass production in large factories. We've all seen cushions with sawdust, newspaper, random bird feathers inside. An upholstered seat may be backed with a discarded piece of cardboard from a KFC box. All sorts of insane garbage.
If someone put a razor there on purpose, that is shitty. I just think it's not likely.