That is technically be true, but I've worked at four shops that have implemented Agile methodologies and it hasn't been true for any of them, nor for most of the engineers I personally know but don't work with. I do personally know one person who works on a team that this is true, but he's the only one.
This may be doing Agile wrong, but if something can be so easily done wrong that it's common, I count that as serious flaw in the methodology.
I'd push back on calling Agile a methodology. [The Agile Manifesto](http://agilemanifesto.org) a set of ideals, that's all. These ideals often run afoul of conventional wisdom in traditional management/business/sales circles, so we end up with a set of procedures masquerading as "Agile" in order to not upset prevailing sensibilities.
You don't have to make big promises when your client has ongoing clear visibility into your progress.