Temporal evolution of the PCA scores for the first two principal components. The PC1 scores (red circles) show an abrupt step-like increase at the profile transition epoch MJD 59781, followed by a long-term linear declining trend. In contrast, the PC2 scores (blue squares) remain nearly constant with no significant variation throughout the entire observational span. A few outlying PC2 points stem from relatively low-S/N observations, consistent with statistical fluctuations and irrelevant to the core evolutionary trend. This demonstrates that the profile transition and its subsequent recovery are dominated by the PC1 mode.