Starch dirtying up a lens or glass is easily solved with a warm damp cloth, starch is water soluble this way. Rice in a port can easily be dislodged without damage with a pin needle. And no particle is going to get into a button in any way that impedes function or causes harm, that’s kind of the whole point of an IP6x device.
But again, we are talking about the company that made trendy the bendy phone, and the “cracked screen and glass back” aesthetic.