For words with a dark L like "milk, help; golf; wolf" etc I don't have contact between the tip of my tongue and the alveolar region. My tongue touches nothing.
However. I have spoken to South Africans who say they do make alveolar contact.
When I read up on L-Vocalisation online, I see that it takes place in England and Australia and NewZealand but there is no mention of South Africa at all.
Is it normal for a small percent of a population to be an exception and vocalise their "l's" when most people in that population don't.