I feel like the Introduction to YAML course could greatly benefit by taking two slight alterations to its current approach.
Structure the chapters and content to copy the flow of information represented in the official documentation, seen here https://yaml.org/spec/1.2/ .
The course should also reference that it is teaching version 1.2 in the unlikely event there is a newer version with different standards.
The quiz questions should provide a direct link to the associated rule in 1.2 spec ( https://yaml.org/spec/1.2/ ). I wouldn’t normally do this for other technologies, but YAML is such a concise and short standard that it seems like referencing the true source would be a good practice.