Assuming a wheel well rider isn't crushed by the gear mechanism.
Assuming they don't fall out when the gear is lowered.
Assuming they don't go terminally hypoxic.
Doubt seriously if a gear compartment would get anywhere close to 300C in normal operations. Freighter brakes do get pretty warm on landing because they are usually landing at max gw for landing, and turn times can be less than 2 hours, but the brakes cool a significant amount by then. Taxi-out heating is something to keep you eye on, but usually not significant.
Getting cooked in the WW compartment? Not sure I believe it, but provocative thought.