I guess we are. According to you, when my cousins go to Six Flags, they're doing fluid mechanics. Forgive me if I don't buy that.
I mean, I get that you don't like that because it proves my point, and that's why you're making really silly comparisons.
But to answer -- yes, most children at water parks also are figuring out fluid mechanics at a simple level, eg drag or interference.
I think there's an important difference between the implicit, intuitive, relational knowledge that we build via direct interaction, and philosophical knowledge that the other poster is thinking talking about (and presumably, what ontology is about). You're equating the two without arguing why we should consider them the same. At best, our implicit model of the world knowledge informs our intuitions on some philosophical concepts, but that still doesn't entail this knowledge is the same as philosophical knowledge.
In the same sense that there's a distinction between counting and mathematics, or throwing things and physics, or conversations and psychology, or various other academic disciplines -- that is to say, a very artificial one.
In every topic, people think about them as a routine course of events -- they just form very simple effective theories on the subject, because their life doesn't require a more advanced one.
"Physics" the academic subject is just a very advanced version of the intuition you build about throwing balls, smashing rocks, walking on ice, and not jumping out of windows.
Similarly, your argument seems deeply confused:
The burden of proof is on the people asserting that an arbitrary distinction in what's clearly a spectrum of things is meaningful. In this case, it falls to you to show that there's a meaningful difference in kind between the sorts of thoughts a child is having about ontology (eg, that a positive version of a shape and a negative version of a shape are the same "shape") and whatever other example you want to use.
Each of you has clearly admitted that they're on the spectrum of ontological thought, because that's why you recognize it so clearly as an example, then just had special pleading of "Well, simple ontology shouldn't really count as ontology, because that would make me wrong."
So again, we see that philosophy is useful -- the "burden of proof" is a philosophical concept that lets me just reply, "No, how about you show that splitting ontological thought into 'true ontology' and 'not really ontology' is useful in the first place."
Except there's a very clear delineation in each case: proper knowledge is articulable, communicable and arguably formal, and in every case of proper knowledge, one can ask "why is that true?", and find a justification that is clear and unambiguous. I can communicate to you a formal understanding of a phenomenon that you had never before witnessed, interacted with or understood, and you can thereby gain a fairly deep understanding of it via this model and make predictions of it without ever witnessing, interacting with or experiencing it yourself.
This is simply not the case with implicit, intuitive "knowledge". The very process of elaborating, refining, and formalizing implicit understanding is what creates proper knowledge.
Implicit, intuitive "knowledge" is to proper knowledge, as seeds are to fruits when evaluating the question of what food can keep you alive. Seeds are by and large not digestible, not nutritious and won't sustain you, but a fruit will. Certainly there is a continuum between the seed to the fully formed fruit, but achieving the status of "fruit" that can sustain your life is definitely not arbitrary.
Discovering shapes is implicit ontology in the way throwing a ball is implicit physics.