The arXiv preprint (abs/2605.26148) outlines a low-cost setup: a water-filled cylindrical glass, graph paper, and red/green/blue semiconductor lasers to measure minimum deviation angles and match them to dispersion theory. Methodology relies on repeated angle readings for three wavelengths only, with no reported sample size beyond the authors' own trials and no statistical error analysis. This remains an unreviewed preprint posted in 2026, not peer-reviewed work. While the demo is visually immediate and replicable, it overlooks how real rainbows involve polydisperse droplet sizes, multiple internal reflections, and polarization effects that the single-cylinder geometry cannot capture. Earlier classroom optics papers, such as those in the American Journal of Physics on prism-based dispersion (e.g., 2018 study by M. Vollmer), already quantified wavelength-dependent refraction but lacked the striking laser visibility this setup provides. A 2022 Optics Express paper on droplet scattering further shows that cylinder approximations systematically understate the angular width of supernumerary bows seen in nature. The preprint therefore strengthens hands-on verification of Snell's law yet risks oversimplifying the transition from lab cylinder to atmospheric droplet, a gap teachers must bridge with follow-up discussion of droplet-size distributions.