None of the material or mechanics that are handled just by the MC are meant to be public. Fronts and Front countdowns are both "behind the curtain" mechanics that are for the MC's eyes only. As the Principles say:
- Make your move, but misdirect
- Make your move, but never speak its name
- Address yourself to the characters, not the players
The substance, movements, and faces of a Front are revealed via your MC moves, which themselves should never be revealed to be merely moves. Revealing your prep material directly does an end-run around the conversation and most of the important game rules that the MC is asked to obey.
Now, this is not to say that revealing these things won't work, since there are as many ways for an RPG to work as there are roleplaying groups. But since you're asking whether these are meant to be public: no, nothing in the MC's hands is meant to be public knowledge. As designed, everything the players know comes to them via the eyes and ears and brains of their character during an MC move, and never are the MC's mechanics revealed.
If you reread the Fronts chapter with an eye for this, you'll find that it's assumed all through the text (emphasis mine):
"The purpose of your prep is to give you interesting things to say." (p. 136)
That's the most important quote. The purpose of Fronts is to give you things to say, not to be a map of the future that the players can study.
"As MC you're going to be playing your fronts, playing your threats, but that doesn't mean anything mechanical. It means saying what they do." (p. 136)
- "A countdown clock is a reminder to you as MC that your threats have impulse, direction, plans, intentions, the will to sustain action and to respond coherently to others'." (p. 143)