Disallow creation of duplicate webhooks

I'm trying to make an integration for bitbucket, github and gitlab.

I found that both bithbucket and gitlab allow duplicated webhooks pointing to the same url,

whereas github will report an error for installing a duplicated webhook.

I think github's behavior makes sense. a duplicated webhook should be disallowed.

I wonder if you actually send out 2 pings to the same url if duplicated webhooks are installed? because this will cause unnecessary workload for my backend.