Autism is manifested in so many different ways and each autistic person is an individual with their own particular personalities, coping strategies etc. Some autistic people are prescribed appropriate medication by medical experts, some are not. Some show a level of "something different" about them that strangers pick up on, some do not. For a young child, the people most likely to know the best way to support them in a public situation
are their parents, and presumably this mum had very good reasons for choosing the lanyard method!
Autistic people are not people to be medicated into societies norms! They are individuals who need support in order to live happy settled lives just like everyone in society.