An undergrad in Physics can dabble in quantum physics and learn some of the mechanics, but the actual theoretical legwork behind it is saved until later. I'd wager that there are few people coming in as undergrads who have (or claim to have) a keen understanding of the dynamics of XY theory that will prove to be valuable. They come in knowing what they've learned from previous education (say, equations and applications of Newtonian mechanics like F=ma), but that's about it. They don't understand the theory that gets the equation; they don't understand the differences in scientific frameworks (they surely haven't read Kuhn at that level), etc.
I'm not sure I agree that undergrads don't know the theory behind it or just have basic understanding - my undergrad degree was in Theoretical Physics and by the time I graduated I had almost 5 years of quantum physics under my belt - about a year of it in high school (the very basics - double slit experiment, wave-particle duality, basic energy levels etc.), then 4 more years of complicated, very in-depth mathematical quantum physics (eigenvalues and eigenfunctions, Heinsenberg's uncertainty principle, Time-Dependent and Time-Independent Schrodinger equations, Pauli spin matrices, Born approximation, 2D and 3D scattering, Dirac notation, entanglement, quantum field theory, degenerate and non-degenerate perturbation theory etc.) - I took 5 semesters of quantum physics at university in total and I did a 2-year research project investigating properties of 2D electrons in quantum semiconductors.
