There is no reason to think that just because the dial will feature some extra cogs, it suddenly needs to be manufactured by ZF to work. The cogs don't even necessarily need to be functional (although it would be a lot cooler if they were), but even if they were, what makes you think they wouldn't be durable enough? You linked some mechanical watches, but you know that those watches can last like 100 years, right? And if you wear a mechanical watch, you also wear it when you are driving your car, where it's subjected to the same conditions.
In either case, everything we've seen from Bugatti so far, including the speedometer blueprint, the latest teaser, even them saying that the interior will be "next level", suggests that the instrument cluster will be analogue. So it's a bit curious to flat out state that it will be digital. That's all I am saying.