For BATCH operations IO transformation extends the operation filter with PK borders by row table partitioning:
BATCH UPDATE ... SET ... WHERE $filter;
...transformation...
BATCH UPDATE ... SET ... WHERE (BeginPrefixSize = 0 OR (BeginPrefixSize = 1 AND PK1 >= $Begin1) OR ...) AND ... AND $filter;
New idea: remove it and make custom PrunePartitions in KqpDataExecuterActor.