Observed and described
partitioned engine execution time difference
between master and slave was caused by excessive invocation
of base_engine::rnd_init which was done also for partitions
uninvolved into Rows-event operation.
The bug's slave slowdown therefore scales with the number of partitions.

Fixed with applying an upstream patch.

References:
----------
https://bugs.mysql.com/bug.php?id=73648
Bug#25687813 REPLICATION REGRESSION WITH RBR AND PARTITIONED TABLES