[abeld]

I would assume the "engineers vs accounts" is due to the output not being intended for the coders, but the managers. I.e. you only have accounts for the managers, but you price based on how large a team they are monitoring.

(This is just a guess, I have no connection to haystack)

[thellimist]

You are correct. Accounts are basically number of managers that can access to the dashboard. Engineers tracked is the main business model.