This diffference in the matching behavior was introduced by 4eab908c8679a797ac7016b77a93ee41bb11b0fc, due to dealing with FC_LANG separately for strong and weak and also difference of looking up order in strong and weak. so lang in strong gives a priority than family in weak.

The following mark is a position of FC_LANG in score. on 2.10.91 or before, family in weak (17 vs 2) is used to determine the better fonts because the score of FC_LANG is same (1), on 2.10.92, former one is used because FC_LANG in weak (2 vs 2002) has different score.

On 2.10.92:
Score 0 0 0 0 0 0 0 0 1001 1 0 2 17 0 0 0 0 0 0 0 1 1e+99 20001 1e+99 1 1e+99 1 1e+99 0 0 0 0 0 0 2.14735e+12 1e+99
Score 0 0 0 0 0 0 0 0 1001 1 0 2002 2 0 0 0 0 0 0 0 1 1e+99 20001 1e+99 1 1e+99 1 1e+99 0 0 0 0 0 0 2.14741e+12 1e+99
                           ^   ^
On 2.10.91 or before:
Score 0 0 0 1001 1 17 0 0 0 1 20001 1 1 0 0 0 2.14735e+12
Score 0 0 0 1001 1 2 0 0 0 1 20001 1 1 0 0 0 2.14741e+12
                 ^