I would say, why not have full doors and if you want horses sticking heads in aisle, have nice openings, so you have best of both worlds?
If you only have a handful of your own horses, sure, let them lean out if that is your preference.
If you have a busy barn with much traffic in front of the stalls, maybe better have a way to keep horses in if they become a problem to the ones walking by, as plenty do under those situations.
A local fellow had some of those first low front stalls I ever saw decades ago in his new show barn.
Later said that was a mistake, he could not use them.
Too many horses were becoming alligators to those passing, that before would have ignored them, feeling safe inside their own place, not needing to or able to defend their space by attacking outside of it.
I agree that the pictures look very pleasing, if standing there pretty is all horses do with open tops.