Yes, the highlighted part is mostly true. As a manager he will be asked about a player (skillset, opinion, others opinions, what he would do on the team etc.) but like any other large organization the decisions are made after that input, including who to trade, who to sign, who to extend. Managers provide guidance on how a player is seen in the industry and how their talents are best used in that industry, just like I'm asked to weigh in on technology approaches at my job and the best tools for them. However I don't carry the weight of those decisions, I am only offering what I can see as what might be a good solution, a solution that is eventually made outside of my realm.
MLB is not a mom and pop store, grab the Reds media guide and look at the dozen's of roles that they have in the FO, the FO and the clubhouse are a different department in the organization, input exists but it is controlled from the top down, not the other way.