It takes one minute and it can be worth thousands to you.
New-home builders in Texas generally pay a buyer's agent only if that agent is registered on the buyer's first visit to the community. Sign in at the sales office alone and many builders will refuse to recognize an agent afterwards — for that community, often permanently.
That is a rule about the builder's commission, not about your price. Registering an agent does not raise what you pay, and the builder does not discount the home because you came alone.
So the only thing being decided when you walk in unrepresented is whether anyone is negotiating on your side of the table.