That sounds awful. The manager is clearly not doing their job well, so avoiding their opinion and covering their mistakes is imho counterproductive. Instead, I would let my reservations be known and proceed exactly as they suggested. If it works, great, I have learned something. If not, let's scrape this and do it right, this time with manager's knowledge.
But in the end, if you can't work with the manager, it's time to head to greener pastures.
But in the end, if you can't work with the manager, it's time to head to greener pastures.