So I’m pretty sure the ingredient angle is out, unless you want to go by proportion of sugar/flour/whatever, which is a much more involved discussion, but IMO, will also be a fruitless one…
I don’t think ingredients are the dividing line here between cakes/breads, IMO, it might be texture/consistency of the loaf, but even that’s a hard sell. There are some very dense breads and some very airy cakes.
I’m more leaning towards “cake” being a label we put on bread products when we deem it appropriate.
The fact that a lot of this was defined by medieval standards, where people did some pretty strange things, especially with naming, IMO, is the root of the problem. Today, as we create new things we have specific terms for them that defines that thing and limits on what the thing is and isn’t. A lot of scientific naming has been refined in the last century because of the bad/inaccurate naming of things, mainly because they were named and defined well before we had the technology to properly understand what we were looking at.
Culinary arts, which can be scientific, but the naming certainly isn’t, is not an exact science. If you take either of the above recipes and add an extra quarter cup of flour or something to either, it probably won’t ruin the product. It might make it taste different than intended, but probably not ruined.
In all the difference between cake and bread is blurry at best. At worst, cake is just a specific type of bread product, which is defined fairly loosely by how we feel about it.
As a related fact, muffins and cupcakes have been in a war for which one is better for you. Cupcakes can have fewer calories, but muffins seem to have better marketing, so people feel like they’re better/more healthy, than eating cupcakes.