How can SMN be the 2nd lowest on total job distribution, but highest on DPS distribution?
I really would like to know how the person doing these decides whether someone is a SMN main or a SCH main and how they do the breakdowns for the SMN/SCH populations. I don't think any of the SMN and SCH numbers are to be taken at face value because the method they use appears to be flawed.
For instance, if you look at A12s clears on fflogs there's 1122 registered entries for SMN and 1486 for MCH (which is the least popular job of them all according to the census). Now you could say it's because MCH is in the speed running meta and SMN isn't which naturally skews fflogs number, which is true to an extent. DRG has 1900+ clears, NIN 1700+, BRD 1485, while BLM has 1300+, MNK has 1200. SMN still is below this by a fair margin.
If anything and even though there's a lot of people who have SMN at level 60 (some of them only by virtue of having SCH at 60), you could say that SMN is under-represented in actual endgame content.
TL;DR: if they consider every ACN 60 playing the game is a SMN, your SMN numbers will be high.
edit: I also remember that adding the % of DRK, PLD and WAR in the last census amounted to a number largely superior to 100% so i don't think they take statistics very seriously.