You're right; I was arguing that French and English are more highly correlated than a pair of languages chosen uniformly at random and therefore easier for MT,

You're right; I was arguing that French and English are more highly correlated than a pair of languages chosen uniformly at random and therefore easier for MT, but I could have made that more clear. I think the difference in accuracy between English <--> French and English <--> German does largely come down to historical academic preferences and data availability, as opposed to linguistic reasons. English <--> French vs. English <--> Mandarin (for example) is a different story.