Imagine biting into a frozen, then thawed, raw potato. It would feel like wet chalk. The texture is completely destroyed. Your mashed potatoes would taste like starchy glue.
Here’s the weird science bit: the starch changes too. Freezing raw alters the molecular structure. It makes the potato sweeter and gummier. You don’t want sweet french fries.
Think of it this way: Ice is a bully. It beats up the potato’s delicate internal scaffolding. The result is a sad, slimy mess that even a hungry raccoon would reject.