Meaning of $cr in dudi.mix for quantitative variables when add.square=TRUE

[sdray]

library(ade4)
example(dudi.mix)
dd1$cr
summary(lm(dd1$li[,1]~as.matrix(dd1$tab[,1])))
## cr is equal to R2 when add.square = FALSE

dd2$cr
summary(lm(dd2$li[,1]~as.matrix(dd2$tab[,1:2])))
## cr is not equal to R2 when add.square = FALSE