That's probably not really even the primary function of it. Nokia comes from a country where half of the year is a weather that warrants using gloves. With just about any current smartphone, you'll have to take off your glove to even answer the call (short from voice commands I guess, but people will frown at you if you do that in public . Same goes for many little things like.. putting the phone on silent/taking it off silent. I wouldnt necessarily start texting with gloves on, but theres a lot of little things I want to check/do without taking gloves off outside.
I dont think the makeshift-stylus idea was based around writing really anyways, cos as you said I doubt it'll have any real support for handwriting kind of stuff, but you can still operate the phone with anything, be it fingernails or just your pencil while you are sitting at school/work/meeting, etc.
I wouldnt look at it as filling some small niche function like handwriting on a phone, but more so as a general huge improvement that allows for a lot more stuff than your generic smartphone screen. The screen and this feature is one of the biggest selling points for me and I didnt really even dream about handwriting on it!
And naturally such weathers mentioned above arnt restricted to just Finland
That said, I did personally suggest some ideas to Nokia regarding this, now that you can make a stylus out of everything, some handwriting recognition and ware down the road could be a big thing. Nokia exclusive, anyone?