I am not necessarily here to debate canonical or good CloudFormation ... I took one particularly unappealing snippet that does not reveal anything that I should

I am not necessarily here to debate canonical or good CloudFormation ... I took one particularly unappealing snippet that does not reveal anything that I should not be disclosing from a bit of AWS provided CloudFormation. Regardless of how you write it, whether you write JSON or YAML, you are writing logic in pure text and the difference between that vs your code going through terraform's solver is night and day IMO. Plus, in source control, I find terraform diffs much easier to grok than JSON or YAML diffs. Especially since with the latter one misplaced invisible character can pass through without being noticed and cause disaster.