Exactly. The distinction is that leadership is something that people voluntarily choose to give to you because they respect you. A manager is a role/job-title.
Many managers are some of the least respected people in their company, and thus aren't effective leaders.
not sure I agree. almost all the time one should lead through guiding consensus and people should proceed based on the fact that they think its the best plan at the time. if thats all the time, then great - you hired very well.
however that process can break down either because there aren't very convincing arguments either way about A or B, or because someone is being unnecessarily stubborn. at that point its fair to step in and say 'we can't make progress until someone makes a decision, and since i'm in charge, thats me, and its going to be B'
if someone was being stubborn, then as a manger you have to work with them to either work supportively with them to get them to be more constructive, redefine their role so they don't get in other people's way, or if those don't work, tell them to fix it or find a new job.
if a manager is just to keep track of vacation time and have motivational retreats, they aren't providing very much value. as a technical leader if everyone feels free to completely ignore the direction you're trying set without even justifying why, it can be hard to get everyone moving in the same direction.
What are you disagreeing with? THe parent said "real leadership should NOT rely on formal authority".
That is, they should be relatively orthogonal (and they certainly have been in my experience; people with formal authority no one trusted, followed, etc, and devs, even on occasion junior devs, who effectively led teams to success)
