@Guybrush85
For what it's worth, you are right about the WAN IP being dependent on the MAC address being presented, so, same third party router, different hubs in modem mode and you'll get the same IP address.
The logs do look a bit of a mess at first glance, but DOCSIS modems on startup run through an entire long list of operations, they need to listen to the data being sent along the cable and work out what they are connected to and which channels they need to listen on for configuration information, then they need to configure the connection, then make required adjustments, then start doing all the IP addressing and routing info etc.
The whole thing does look like a complete mess but they get there in the end. But until all of this is done there will be an entire slew of 'critical' errors and messages which is all normal as things just haven't got themselves into a functional state yet.
It does look as if the Hub 5 is much more verbose in what it logs on startup, if you take a look at the log you posted earlier, all of those errors etc. all happen within the space of less than two minutes until it finally logs that it has managed to register itself properly and is just waiting to come fully online - so the startup process hadn't actually completed then, but it's nearly there. I do suspect that as the Hub 5 becomes more widely rolled out, we'll be seeing quite a few posts on here from people seeing all these 'errors' etc. and assuming that there is something badly wrong.
Your earlier BQM did look a little spikey but nothing too badly off, the upstream QAM will adjust itself up and down to compensate for noise issues which is how it is designed to work.
John