Support doesn't officially support third-party products, and support engineers may or may not know Terraform. Engineers definitely aren't trained on Terraform, and your mileage will vary a lot depending on the specific engineer and their background. It really depends on whether they've run across it in other jobs, personal projects, etc.

Customer obsession is a big deal for support engineers. So if they can, they'll try to help solve a Terraform issue. But it'll be on a personal, best-effort basis.

For such a mud-slinging article, I'm surprised the author didn't complain about the most pressing issue (IMO) with CloudFormation: There have been a few instances where thing in AWS changed and Terraform was updated more quickly than CloudFormation was. Happens less and less now though.