If SAM relies on Cloud Formation, there must have been some serious changes at AWS. CF was/is notoriously lagging behind AWS console and API in terms of feature coverage.
The Terraform AWS provider has always been much faster to reflect the AWS API changes.
The place that suffers is ElasticBeanstalk. I used to be on EB but couldn't take it anymore. I kept having to run mini-templates from inside the beanstalk machines to get access to specific items that weren't exposed to CF directly.
Once I moved to ECS/Fargate, it's worlds better support. ECS still has some parts that are laggy in the CDK (and you can still do it via JSON obj) but not in CF. It's been pretty good here in Fargate land.
But in this case it wasn't Hashicorp fault, as what was available in CF wasn't in the AWS official API.
It took something like a year for AWS to release the API