That may be true. I'm checking it out with my original Porsche friends and historians, just to get a second opinion.
My late brother's '57 Speedster was a 1500 normal, not a Carrera, but, in 1965 when it first showed up in our garage, it had already gone through a few "improvements", mostly in the handling department, not usually in exterior "bling".
I've asked the TYP356NE club technical guru to weigh in on this and will report back (he drives a pristine 1955 original Speedster - Pearl's 'poor cousin', if you will). If anybody knows, he will.
Also, don't forget that Max Hoffman always had cars in the pipeline, so to speak, and there is a bit of overlap in years versus models sold - meaning that there were Speedsters sold in 1959 as '59 Speedsters, as well as Convertible "D" models in 1958 and 1959 before they were replaced by the "Roadster". As far as I know from researching my brother's car, there were 47 Speedsters imported/sold in the US in 1959. As you might imagine, it's harder to tell if they were already here, or actually arrived here in 1959. PLUS, you don't know what options were dealer installed (lots) versus factory installed (few).