Per-Minute Ratings refers to normalizing any counting statistic to a per-minute basis (e.g., points per 36 minutes, rebounds per 48 minutes) to enable fair comparison between players who play different amounts of time.
The basic normalization principle is sound and necessary. A player averaging 12 points in 24 minutes is contributing at the same rate as one averaging 24 points in 48 minutes.
Per-minute stats are vulnerable to minute sample size effects: bench players who play garbage-time minutes against weak competition can have inflated per-minute numbers. Quality of minutes matters, not just quantity.
The per-minute normalization principle is embedded throughout APEX — z-score normalization, TS%, AST%, REB%, and the RAPM-family metrics all normalize for playing time in various ways. APEX's GP^0.75 availability modifier applies a smooth penalty rather than treating all minutes as equal. Per-36 or Per-48 raw counting stats are not used as scoring inputs because they don't adjust for opponent quality or usage context.