This is true, but it is really a distinction without a difference. The history I use (Vieira's Pieces of Eight) indicates that, "The draftsmen of the Coinage Act of 1849 were careful, therefore, to refer to the 'gold dollar' not as a dollar or the dollar, but as 'be[ing] of the value of one dollar.'" (Vieira's emphasis)
ML/NJ
Truly the history of US coinage would have been much happier had there been no statutorily fixed connection between the value of a gold eagle and a silver dollar (letting the market set the respective values between the two). However, the reality is that Congress did define the dollar value of gold coins.