I watched that video. I prefer the current (julia’s) behavior, comparing to other languages.
Yes, dot(x, y) calls BLAS, which is specialized.
Looks like sum(x .* y) will call mapreduce and therefore resolves into standard + and * operations (perhaps calling standard C functions?).
Moreover, it appears that dot(x, A, y) also outperforms x' * A * y, at least in terms of allocations, sometimes also in time (can someone do a test?).