Interesting. I have the same model as you used (MB7220) but port 8080 appears to be closed (connection refused). In fact, nmap shows no ports except 80 are open. I guess a firmware update took that out.
Mine reports version 7220-5.7.1.15 in the admin console. I would be interested to know if anyone else is able to access it.
I use this modem for my internet service so unfortunately I can't just take it apart to replicate this experiment!
And this page confirming they can still be detected: https://www.kg4cyx.net/the-oddball-embedded-spectrum-analyze...