The physical distance between woofer and tweeter causes the sonic axis of the speaker system to be angled. (The ubiquitous MTM driver array avoids this). So, by positioning the speakers at an angle, the (small) effect of having the tweeters inside or outside can be counteracted.
However, the direction of the sonic axis deflection is such that having the tweeters outside is equivalent to positioning the speakers angled in. This means that you can probably leave them physically straight, and from a cosmetic point of view this may be desirable.