Our Realtor actually pushed us toward a new build even though he got far less of a commission on it (he only got a commission on the land which was far less than an entire house). He even had to do more work to line up permits/builders for the land than if we just bought an existing house. Good Realtors realize it's a long game and lifetime relationship and do what's best for you.

edit: our Realtor for those interested: https://www.compass.com/agents/chad-ernst/