I've worked on IT development projects for 25 years in various technical and analytical roles, using both waterfall and loosely hybrid waterfall/agile methods. They've always had a planning phase up front, to work out a list of tasks, which we would estimate effort against, and that would give the overall timeline for the project. If a task took longer than expected, then it would push the timeline out. This was all very visible on the plan. But ...
A new senior leader at my organisation has kicked off a "transformation programme" consisting of more than a dozen inter-related projects. He has hired some contract project managers to help with delivery, and the one I'm working with has been set a deadline of delivering a complex new system within 6 months. My high level estimate is that it will take at least 18 months (and probably more, as many of the people we need input from are working on multiple projects at the same time). Whenever I suggest creating a task breakdown and putting estimates against each task I'm brushed off. Whenever I say I don't think we can meet the deadline I'm told we have to "challenge ourselves". The contract PM has been presenting highlight reports to the senior leader that suggest everything is on schedule. The senior leader doesn't know enough about IT development to question them. This will unravel very soon, and no doubt those of us on the project team will be blamed for not meeting fantasy deadlines. Is this how "right to left planning" generally works? I know it can't be - I suspect the PM is just naive and is sadly trying to stay on the right side of a senior leader who is deluded.