It doesn't matter how many times Ava or the others says that Julia will never be an option, that the game won't have incest content, some people still cling to the idea that somehow Mr Jet is just trolling everbody and that Julia is a secret route just like in those old school RPGs that you had to do a thousand of different stuff, play the the game in specific time of day or the week to magically unlock it the secret route or ending
Here's some thoughts on this,
1. I prefer such info coming from a dev and not another player, no matter how well established she or he is here on the boards.
2. because, sometimes players just don't know shit. Fe. over at "Where the Heart IS," many players including Ava are dead-bent on telling everybody that there is no harem route, that you can't end up with all the main girls. However, Cheeky never actually said that, when asked about it he just answers he doesn't want to spoil the matter and in the last one or two updates, he even made some small jokes about how a "cheeky god" might be the only way to achieve that goal. Not saying it will be possible, but I also wouldn't rule it out for now.
3. Even if a dev states that a route isn't going to happen, they are known to sometimes change their opinion, fe. through noticing how many players would want to see that specific option. Women go from side characters to main LIs, planned main LIs are cast aside, because they have no support among players.. etc.. I have seen all of that in games here.
4. Just recently "My Sister, My Roommate" ended and practically since the start many people had asked for a sister route, alas, it wasn't going to happen, in fact, instead of adding another route, the dev removed all but one, really. And there was backlash and lots of negative reactions to that decision and now he has decided to get back to work on the game and include more possible endings. Still not sure there'll be a Nikki ending now, but at least Sumodeine has finally recognized, in his own words, that it was wrong to cling to not making the sister route, just because he at one point said so and stubbornly ride it out.
I'm paraphrasing, but that was the point he was making.
Now, I'm not saying we need a sister route here, nor that the people giving the negative answer are misinformed or that the dev should be persuaded to change his plans, just that it's not like it makes no sense to tell Mr. Jet what you want. Opinions and games can deviate from the initial version.