JP, If the default as pulled up by the current version of the webhook/integration is incorrect then with respect you need to do something about highlighting that in the Forum vs just a belated ‘go read the docs’ message. 
What I see is
I assume this is incorrect, that you have fixed with the TTI core team, and that yes there is a release cycle and users will get corrected version ‘soon’…
But, when was problem identified? When was fix issued? What has been done to communicate this to users - casual or otherwise? And before anyone shouts ‘use forum search’ I just did that and a) wouldn’t know to look/search for a problem as not aware of one and nothing mentioned previously and b) a search for either of the url versions listed above only calls out one thread - this one - where we called them out above! 
Users of V2 clicked the TTNMapper integration and data automagically appeared on the map, there is no reason to assume that on the V3 console they had to do anything different and they have to go read a different set of docs instead …unless you tell them. 
I believe it has been previously suggested that you amend the TTMapper site to call out a specific link to the docs. At the moment all users see is:
The “please read here” links to the “migrate GWs last” thread on the TTN Forum, and even in the FAQ, the only link to documentation is a link to the doc on TTN - not to any specific TTNMapper docs! Casual users have no obvious way of knowing they need to go searching somewhere else.
For anyone who saw the original posts or who now are looking at adding TTNMapper Integration via V3 Webhook please go in and modify the default url as shown in the image above and correct it to
As highlighted by @engelking above
Until TTN V3 CE receives appropriate update to correct the error.