I would not want to make that assumption, although it may be correct, of course.
I wonder how many setters don't even know that there is an alternative spelling that will fit the pattern.
In the particular case today, I did not know that there are two spellings. But I now see that, because of the way the clue is worded, another (distinct) type of pasta would fit and would answer the clue.
So, if I am reading it correctly, it is not so much an alternative spelling of the same thing, but an alternative thing.