Unexpected (?) behaviours when using bind_rows() on different classes

[LeoRoth]

Bind_rows() behaves differently when used on columns of class numeric and factor or integer and factor. In the first case it converts the resulting column into numeric and in the second it fails. It is even more confusing that both behaviours are different than when using rbind(). In my opinion the rbind() option (converting to character) is the most appropriate. Thank you deeply for all you work anyway!

library(dplyr)

df1 <- data.frame(a=c(1,2), b=c(1,2))
df2 <- df1
df2$b <- as.integer(df2$b)
df3 <- data.frame(a=c(1,2), b=c(1,'q'))

# column b is numeric in df1, integer in df2 and factor in df3
bind_rows(df1, df3)
bind_rows(df2, df3)

rbind(df1, df3)
rbind(df2, df3)