STATISTICS IO for parallel index scan
If you add a TABLOCK or READUNCOMMITTED hint to the table, you will get an allocation-ordered scan, which will report the same number of logical reads as the number of pages in the table.

With an allocation-ordered scan, SQL Server uses allocation structures to drive the distribution of pages among threads. IAM page accesses are not counted in STATISTICS IO.

For a non-allocation-ordered scan, SQL Server breaks up the scan into subranges using index keys. Each internal operation to find and distribute a new page, or range of pages (based on a key range), to a worker thread requires accessing the upper levels of the b-tree. These accesses are counted by STATISTICS IO, as are the upper-level accesses made by worker threads when locating the start point of their current range. All these extra upper-level reads account for the difference you see.

Too much weight is given to I/O statistics in my opinion. Tune your queries according to what is important to you and your workload. This is often elapsed time, but resource utilization can also be a factor. No one metric is 'best' - you should take a balanced view.