Second, the top 1M of 6/7/8 character passwords have a statistically higher probably of being the correct password than the top 1M of 62^12 because their distribution function as a percentage of possible instances is narrower. Put another way: the top 7 char password might be used 10 million times, and the 2nd most popular might be 9million, etc. With a 12 char password, the top 1 by nature appears much less frequency because the total possible space is larger and people have to think a little more. Entropy when that has nothing to do with inverse distributions.
Put another way, look at the frequency of the top-1 password as a sum of all instances of all 1M passwords. It is much larger % for smaller passwords than larger. It is much less likely that the top 1M 12-char passwords are as likely to be successful as the top 1M 6/7/8-char passwords.
I just did this for the top 1000 6/7/8 chhar passwords, the top 6 digit password "123456" represents 1.3% of all 1000 6-chars, where as "password" is 0.9% of all 1000 8-char.