Coherent perfect absorption: Zero reflection without linewidth suppression

Motivated by recent claims, we revisit how coherent perfect absorption (CPA) influences cavity and polaritonic linewidths. Using standard input-output theory and measurements on single-port bare microwave cavities and cavity-magnon hybrids, we find that CPA drives the on-resonance reflection amplitude to zero while the spectral width remains set by the total decay rate. Apparent narrowing observed near CPA is found to be a visual artifact that does not remain upon quantitative analysis. Extending the analysis to cavity magnomechanics, we show that logarithmic plots can exhibit apparent polaromechanical “normal-mode splitting,” whereas linear-scale spectra display no true splitting. These results clarify when CPA modifies amplitudes versus spectral poles, offer practical guidance for data presentation, and indicate that CPA alone is not a route to linewidth suppression or polaromechanical mode splitting in the linear, weak-probe regime.