Not a bug. The "Current Hacksteak" shows how many days you have already gotten in the 7-day hacksteak. Once you complete a 7-day hackstreak, the Epoch medal gets +1, as you have completed a hackstreak.
The Current Hackstreak is "days", the Completed Hackstreak is "weeks" (effectively).
Meaning to say I need to hack 7 days straight to get 1 epoch count?
Yes. Only a full seven day streak will tick up the Epoch counter.