I don't think you can ever permanently "brick" something. In this case they probably reflashed the firmware through the JTAG port or something similar. Bricked to the consumer but not the supplier.
You can permanently brick a device, even without hardware damage. Phones, for example, should have JTAG completely disabled for security (though many OEMs fail to do this), and depending on various bits of low-level config devices can get into a completely unflashable state. If the onboard firmware that accepts flashed images does something like sign the images with a key embedded in the SoC, and the ROM refuses to run unsigned firmware, and you can't flash normally any more, then even removing the flash memory and writing to it directly may not revive the device.
Plus, software can sometimes do hardware damage, which can perma-brick.
But, yeah, in the vast majority of cases where a device is "bricked", it can actually be revived by the manufacturer or their RMA centers. Even if JTAG isn't available and the system is tightly locked down, they typically have some keys they can use to sign messages to disable portions of the security infrastructure, specifically so that they can revive (and resell) bricked devices.
I do low-level Android development and end up bricking a few devices every year. It's pretty rare that they can't be revived by the manufacturer, but it does happen.