Counting from flip is what most growers and breeders tend to count from. It is actually the only way of counting that isn't open to personal interpretation. I have yet to see a strain suddenly sprout the white heads of flowering within one day.
Your buds look great. A ton of strains do not put their bulk on till the last week or two. Also those do not look all that small. I agree with the 2-3 weeks to go. But I also am not looking at the trichs.
Cheers