According to previous studies by our group on hydrogen-related vibrations, CNEO-DFT harmonic analysis can reduce errors by 90% compared to conventional unscaled DFT harmonic analysis. Furthermore, although VPT2 may face challenges with strongly hydrogen-bonded systems or shared-proton systems, the hydrogen bond in Type IIa proline is comparatively weaker, with its expected vibrational frequency being above 3000 cm⁻¹. Therefore, VPT2 is reliable for this system. The agreement between the CNEO-DFT harmonic frequencies and the corresponding VPT2 values indicates that this assignment is robust. However, to achieve even more accurate results, we additionally performed CNEO-MD simulations. Compared to CNEO harmonic analysis, CNEO-MD can better capture mode coupling effects through thermal motions at finite temperatures and therefore yield more accurate peak positions and qualitatively correct peak broadenings; 69-71 however, we acknowledge that the descriptions of overtones, combination bands, and Fermi resonances are still challenging and that high-level quantum methods, such as MCTDH and VSCF/VCI, are still needed for accurate descriptions of these subtle features. The improved performance of CNEO-MD over CNEO-DFT harmonic analysis is usually more significant for hydrogen-bonded O-H stretch modes, which often couple strongly with some lowfrequency vibrations, than it is for free O-H stretches, which have relatively weak couplings to other modes.