all.equal only reports differences in first column with differences

[BartJanvanRossum]

When comparing two data.tables with differences in multiple columns only the difference in the first column is printed.
See the code below:

dt1 <- data.table(A = 1:5, B = 1:5)
dt2 <- data.table(A = 2:6, B = 2:6)

all.equal(dt1, dt2)

df1 <- data.frame(A = 1:5, B = 1:5)
df2 <- data.frame(A = 2:6, B = 2:6)

all.equal(df1, df2)

I expected similar output printed as when using all.equal on two data.frames, i.e. both columns that have differences reported. The latter is also what is described as output value for the function.