Groupthink is when people, seeking validation from a group and to preserve harmony and cohesion, withhold their opinions causing the group to make suboptimal decisions.
If you think you will have to do this, don't join the company. Groupthink means the company doesn't foster psychological safety, which is the top predictor of team performance.
This is not only bad advice, it's probably unethical too. You are expected to work in the best interest of the company, and the company is expected to not punish people for speaking up about their ideas.
What you described works if you want to advance yourself at the expense of the company, but again, it is not ethical.
You are just exploiting information asymmetry, and anyone that likes doing that in a good faith organization should be let go. Highly political people are a waste of time.