Agree on the second point. I tried to convince some managers and sales guys to stop giving estimates at all and build trust otherwise, didn't work :)
As for consistent, my point was if you have 100 SP in backlog, delivered 50, then I contend you are not in the mid-point of the project. This is a dangerous assumption. You don't know where you are in my experience.
It is if you're following agile principles. By the time you've completed a few stories you should be delivering every feature at production quality with all the automation pipeline and deployments ready. The question from that point is always did we build enough features for a launch.
As for consistent, my point was if you have 100 SP in backlog, delivered 50, then I contend you are not in the mid-point of the project. This is a dangerous assumption. You don't know where you are in my experience.