I disagree. For example, the Wright brothers did air foil engineering empirically without full knowledge of the underlying fluid mechanics. Early and innovative engineering will often be less based on existing scientific or mathematical knowledge, while still using some of the methods. It's still absolutely defined as engineering.
It was always engineering. You're making the assumption that their theories are not rooted in anything coherent at all, but almost always this is not the case. Usually a "what if we..." thought is based on other knowledge, and there's absolutely nothing wrong with trial and error... this is what research and experimentation, areas of science, are all about.
Of course it is. The science comes from reproducing what you tried and getting the same results.
You may not have a good enough model for this observation to allow you to predict the results of other starting conditions, but it’s a model nonetheless, one that narrowly applies to the conditions you tried.