It also matters what "scientific principles" we are talking about.
In software its more philosophy rather than hard facts. Otherwise you would not have eternal debates about Object oriented versus Functional programming, to name but one example.
The link with the physical world makes true engineering disciplines more objective.
Everything in software is a hard fact. In fact I would say it's even harder since we can measure everything to pretty minute details if we want to. Something that is much harder in other engineering principles. Software is just as bound to the physical world as other engineering principles. For example you can't just write a O(n!) implementation and expect it to work.
Ok, you are obviously using language loosely. There are some hard facts in software but they are mathematical (logical) not physical.
In fact in various languages software has connotation of working with logic (logiciel in French) or information. I don't have an overview but in many languages computer engineering is associated with hardware and the programming side is some variation of informatics or programming.
Unless I hear something more insightful the working hypothesis is that the term has come to be seen as more dignified than mere "programming" because it implies a more abstract, scarce skill set. So its abuse is a sort of title inflation similar to everybody becoming a "VP". One could equally well have assumed that computer programmers (or developers) do have those skills.
Anyway, as far as I am concerned programmers can call themselves doctors, prophets or supermen, just curious how and why the term "engineer" has been overloaded from its previous hardware association to over time denote purely programming activity.
"Engineering is the use of scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings."
Seems to align pretty well with building software.