AWS launch template create-before-destory?
It seems you're misunderstanding what the create-before-destroy lifecycle parameter of the launch configuration does.
It's about replacing the launch configuration within an autoscaling group, not replacing the autoscaling group.

Launch templates have versions which makes this parameter useless as you'll create a new version of the launch template before updating the ASG to use it.

Terraform gives an example in the ASG documentation.

The underlying idea is to be able to roll back more easily than with launch-configurations.