It's possible they could both be right. It just depends on how the draw length is being adjusted.
If it's being adjusted by changing a draw length module then it will not affect the draw weight, in which case the dealer is right.
If the draw length is being changed or tweaked a bit by twisting the string or cable then it will change. Add twists to the string and/or untwist the cable and the draw length gets shorter, and the draw weight will become less. Twist the cables to shorten them and/or untwist the string and the draw weight will go up.
Most often, and I think the is is the case, you are referring to changing a draw module. I only added the second part in case someone wants to be more critical.
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