Is a temporal annoyance because managunz has not been updated yet to add specific HEN support
When managunz boots it does several checks to know which firmware you are running, and the presence of other custom code running as cobra, mamba, different syscalls, etc...
Based on that checks it shows to you different options availables to mount games
The option mentioning cobra should appear
only if you are running a cobra firmware (but HEN is not cobra)
I think what is happening is managunz thinks you are running a cobra firmware because there are some syscalls active... lets say "it looks like cobra" (but is not cobra)
So i guess that text string mentioning cobra needs to be modifyed for the next managunz version, and it will show a sentence mentioning HEN
Is a minor detail, the sentence is wrong but is just a visual annoyance, in the meantime you can modify that texts in managunz as explained here:
https://www.psx-place.com/threads/managunz-hen-support-feedback-needed.23891/