The agent at a builder’s sales office works for the builder. They are pleasant, they are knowledgeable, and they are not representing you. Most builders will only pay a buyer’s agent if that agent is registered the first time you walk in — visit once alone and you can lose the right to your own representation on that community entirely, at no saving to you.
I am also a Certified Residential Building Contractor, which changes what a buyer’s agent can do on a new build: read the contract’s allowances and change-order terms, tell you which upgrades hold value and which do not, and walk the house at framing and at pre-drywall while problems are still cheap to fix.