Hi, @mainhawq. The behavior you are seeing is most likely explained by downstream resolver caching. There is a support guide with more information about this here:
There is nothing we at Netlify can do to purge the downstream resolver caches. The solution is to wait for the cache DNS records to expire and they will be purged from the resolver caches at that time. (The admins of the resolvers can purge the caches but there is no reasonable way to contact all admins of all resolvers nor would most of them have the time to do this for you and your domain. The solution here really is to wait.)