True! But it still hurts the resale value because users are likely to notice a device with broken secure boot if you were to somehow use it to forcefully flash a modified ROM.
Are you proposing this mode could be used to somehow clear the secret data?
My understanding is EDL mode can refuse to flash some partitions and some devices will not enter this mode if fastboot is working, which also enforces preventing access to some partitions. Most people who use EDL already unlocked the bootloader, but I don’t think this method works on all devices if the boot loader is still locked.