Hi The Koalabat,
My name is Josh Wells and I am a support engineer on the Microsoft Dynamics CRM Support team. If the report is doing what you want it to do, then you did it right. There is not necessarily a right or wrong way to do it. It's all about preferences and what you are comfortable with. The developer you previously worked with may have used a standard parent report they use for most of their reports and then created a sub-report for your particular request.
I'd say you did a great job if it works as intended and this was your first report with FetchXML and LinkEntities.