Does washing reduce asbestos?
The article that you linked to in your first bullet seems to be aimed at people who happen upon asbestos during day-to-day life by accident, one-off cases like in your experience. It is not meant to provide a guideline for people who work in the asbestos abatement industry.

The accepted answer linked to in your second bullet (and the question itself) is aimed towards people who are working with the removal of asbestos as a job. These people are in much more contact then a one-off small exposure such as your case. While the highlighted quote that was shared from the Australian government's guideline says that no clothing is to be washed in an worker's house (the employer should be taking care of this), the guideline also says:


  Laundering of asbestos contaminated protective clothing is not
  recommended, because decontamination cannot be guaranteed. The
  otherwise reusable coveralls etc should instead be disposed of as
  asbestos waste.


Again, this is the case for someone who is working with asbestos daily, their clothing will be highly contaminated.

If I was you, I would not be worried about the sweater or the other clothing being contaminated.