I cannot comment on those posts. I’ve done several updates on three different Onkyos, a Yamaha, a couple of TVs, Macs, Windows PCs and various other devices over several years without bricking a single one of them.
Backing up and then uploading firmware to an Onkyo is a bit more easily done with an ethernet connection as the wifi connection would need to be reestablished before performing an upload after a factory reset. The backup/upload of settings can only be done using the web setup feature of the Onkyo.