Their reverter doesn't appear to have any brick code, but it does appear to have several failure points.
First off, it uses the flash to detect if it is actually the right cart, and appearantly uses a hash of a portion of the flash in some crypto. So, if your flash isn't exactly as they expect it to be, it won't detect it.
Second off, it erases and writes to the entire cart. If something goes wrong, poof goes the data that should be there.
(As a few funny sidenotes: They applied crypto to their flash file, and then decrypt it before flashing. 1. they left in the code a debug feature to dump the decrypted stuff to file, so if you wanted you could patch it to trigger the debug feature. 2. This doesn't even matter if you know how to read from flash -- they didn't bother to try and obfuscate their reading/writing code, so... )
Meanwhile, we're working on support for these carts in flashcart_core/ntrboot_flasher. Reading works for sure, writing works on a related cart (r4isdhc.com), ntrboot injection isn't implemented yet.