Thanks for the article.
As a reminder, if you use an account to run setup that has domain admin permissions (lets face it, this will apply to more people that we care to admit), the object creation limit will not apply. Another well documented cause for 19471 to consider is a change to the default location for new computer objects. If IT or Systems Engineering (whoever maintains A/D) likes to compartmentalize stuff, it is possible that the cluster computer account will be in a OU container where it, itself, won't have permissions to create new computer objects (AG name). Since AG configuration uses the user login account as proxy for access, it may not be object limit. Microsoft makes mention of this. All you need to do is check with A/D administrators and ensure that the cluster account has permissions to the container in which it resides at least for the duration of setup.
Basically, user login is used as proxy to create new cluster computer object:
User Login > (has access?) > Create Cluster > New Cluster Computer Object (in container)
Then, cluster computer object (now not a proxy of setup user login) will attempt to create AGL:
Cluster Computer Object > (has access?) > Create AG Listener Computer Object (in container)
The gotcha is the (in container) part. If the location for new computer objects is not default, then the Cluster Computer Object may not have permissions to create the AGL.
Good luck and welcome to the world of Availability Groups!