When doing analysis on exceptionally large sets of numbers, it is common to round to the closest even number, instead of rounding up. This is so that the average rounding of the .5 values will be 0, rather than .5, which can skew the overall results upwards.
This definitely accounts for #2. You learn something new every day.
As for #1, this appears to have been fixed. I now see 6.5's correctly in game rating lists.