gtid_current_pos is the union of gtid_binlog_pos and gtid_slave_pos. RESET MASTER resets gtid_binlog_pos, but it does not reset gtid_slave_pos. This means that new GTIDs added to gtid_binlog_pos can actually lag behind the GTIDs in gtid_current_pos after RESET MASTER is executed if gtid_slave_pos is set and if it contains GTIDs in the same domains as the ones in gtid_binlog_pos. This should be added to the documentation.
MDEV-17156 for details.