Without knowing exactly what is required for making su filindeu, the video of Paola Abraini looks to me a lot like a la mian maker in training. I wouldn't be too surprised if a la mian chef picks it up right away and starts making su filindeu ten times faster than she does, instantly turning the "rarest pasta in the world" into "a pasta from Sardinia".

https://www.youtube.com/watch?v=rHGZLjJ1CAk&t=40s

In the spirit of famous-English-chefs-unable-to-make-thin-noodles, here's Gordon Ramsay unable to make la mian: https://www.youtube.com/watch?v=GaeyFyQemDw

Do they always cut his shows such that it's impossible to tell what's going on, or is that one just extra mutilated?

I'm actually incredibly interested to know if su filindeu is historically linked to la mian in any way (apart from the obvious pasta came from China argument)

It didn't come from China: http://www.bbc.co.uk/news/magazine-13760559

It's not exactly impossible that both arrived at something similar independently.

Your link describes the arabs bringing it to Sicily somewhere around 8th/9th century. So? Do we know they didn't get it from China? Of course Italian pasta is unique, it has had ample time to develop its own culture around it, but I've never seen evidence that the initial idea was born in Italy. It would be a bit like the Japanese claiming they invented Tofu. Well, no, but does it matter?