Why does the bedtime move before the alarm?
Because cutting sleep is what makes early alarms fail. Two weeks of moving the bedtime first means you're building a surplus, so the first early alarm doesn't land on an already-short night.
I'm exhausted at 6am even after eight weeks. What now?
Either your bedtime is too late for the sleep you need, or something is wrong with the sleep itself. Loud snoring, gasping, or feeling wrecked after eight full hours all point at sleep apnea, and that's a doctor's job — no habit plan will fix it.
Do I really have to keep it up on weekends?
Within about 45 minutes, yes, at least while you're shifting. Once 6am is established, the odd late Saturday costs you a rough Monday and nothing more.
What if my job or kids make a fixed wake time impossible?
Then a fixed wake time is the wrong goal and the plan should be built around your real constraints. Tell Mosey the actual shape of your week and it will aim at something you can hit.