Description
After SPARK-35725(https://issues.apache.org/jira/browse/SPARK-35725), we might expand partition if that partition is skewed. So the partition number check `bytesByPartitionId.length == partitionSpecs.size` would be wrong if some partitions are coalesced and some partitions are splitted into smaller.
Note that, it's unlikely happened in real world since it used RoundRobin.
Otherhand, after SPARK-34899(https://issues.apache.org/jira/browse/SPARK-34899), we use origin plan if can not coalesce partitions. So the assuming of that shuffle stage has `CustomShuffleReaderExec` with no effect is always false in `REBALANCE_PARTITIONS_BY_NONE` shuffle origin. That said, if no rule was efficient, there would be no `CustomShuffleReaderExec`.