Some part–whole cases also invite discussion about established linguistic convention. A broad word may become customary for a particular relevant part, while another analysis regards the same occurrence as figurative transfer.
The aṣābiʿ/anāmil example can be understood rhetorically as naming fingertips through the full fingers; however, the exact classification also calls for attention to the accepted ordinary use and the specific context.
The point is not to eliminate the rule, but to recognize that lexical assignment and occasion-specific transferred meaning must be distinguished in careful analysis.