The newest bitmain firmware disables ssh on boot, therefore you can not ssh into machines. Its not a big deal if you have a few machines, but there are many farms out there with hundreds or thousands of miners that automate configuration and reboots using software, this new firmware removes the ability.
They quote "security", but its bologna. Why not give the end user a choice to turn ssh on or off through portal. Any end user with a couple machines can turn ssh off, and farms that tunnel through firewalls can leave it on, our choice. They are purposely making larger mining operations lives harder to get an upper hand.
You can do all necessary configurations, get kernel logs, do reboots etc. all through the cgi pages on the web portal. It is actually much faster than SSH on these miners because they always sit for a few seconds before you can connect via ssh.
Large mining operations can easily have someone to tweak their scripts and how they do configurations. However, unexperienced and smaller users who are clueless could easily get an ssh virus if any infected miners or control boards are put on the same network.