When you exceed the maximum the manufacturer recommends, damage may occur. It's unlikely to happen very fast at 453°C compared to the maximum of 452°C but it is not good for the unit. At higher temperatures damage will occur. Examples include, but are not limited to, melting of the solder used to assemble the Peltier module, damage to the semiconductors themselves and damage to wire insulation and damage to the fans.
The module with its semiconductors itself is probably not rated for more than 200°C so the product depends on the fans running. The fans are probably not rated for more than 70°C so the fans will be destroyed unless they cool themselves. Hence all the warnings about how the fans must be spinning. Clearly, if you put that device into an oven and bake at 452°C it will be destroyed.
Engineers typically don't like operating devices near the 'maximum' as usually there is some grey area where lifetime will be compromised. Brief excursions to close to the maximum and sometimes even beyond may be acceptable (for example, during soldering we typically exceed the maximum storage temperature of a device), but usually we like to stay well away from limits.