Final answer:
The statement is false; whether U-Boot saves environment variables on reboot depends on the configuration. Some systems may save changes automatically, while others require the 'saveenv' command.
Step-by-step explanation:
The statement is false, not all U-Boot configurations save environment variables upon reboot by default. U-Boot's environment variables are stored in a non-volatile storage area, and whether or not changes are saved automatically depends on the specific configuration of the U-Boot build. Some systems are set up to automatically save any changes made to the environment variables, but others require the user to explicitly save the changes using the 'saveenv' command. Without issuing this command, any modifications would be lost upon reboot. Therefore, it is critical to understand the configuration of your specific U-Boot setup to determine how environment variables are managed.