It seems to me like it is intended as a "complication", rather than an afterthought.
It is more difficult, in my opinion, to place correctly the incomplete fragments so they do not look unnatural to our brain, that tends to "see" and "read" a complete number regardless of whether it is wholly or partially represented, provided the fragments are exactly placed in space. Placing a dot may look less "disturbing", but it is also a little easier.
Incomplete numbers do not bother me in a pocket watch, but generally I prefer complete numbers in wristwatches.
Apologies for reposting this pocket watch photo. It does have some connections.
I would be interested to know what the history you refer to is in regards of an incomplete number six.
Regards