:Heh, I remember asking this question a couple of years ago when I was newer and having a great deal of trouble getting any kind of "rule"-oriented answer. I have a vague recollection that I found something I could point to, but if I did, I can't find it now. Then, after a while, I realized it was fairly standard, at least for experienced editors, to remove pre-production films from tables, so I just forgot about it and automatically do it. I see people cite to WP:CRYSTAL, but that, of course, doesn't specifically address filmographies, so it's a much more generalized and fluid concept and ultimately a judgment call. Some even cite to WP:NFF,even though it's a notability guideline, for the notion that if you can't have a film article about a film that isn't in production, you can't have an entry in a film table, either. Not altogether satisfying as someone may always point out that notability doesn't affect content, just creation. 

 :I keep thinking that if I search hard enough, I'll find something, but the closest I came was a discussion I was involved in with no good answer from WP:FILM. 

 :Sorry. If you do find anything, please let me know; I, of course, will do the same.