Does selecting Grayscale automatically convert to PDF?

[vixler]

I created a PDF of black line art. The art was created using an app that only has RGB. I then put the PDF into Acrobat. and in Color Convert Tools I selected Grayscale as well as the options "Preserve black" and "promote gray to CMYK black."

Whether or not it was converting the whole document to CMYK was unclear. That second option implies it, but does it mean only "grays" or also blacks? And does the fact that the lines were black RGB mean they are  blacks that get "promoted" to CMYK, or if it is "preserving" blacks does that mean it is preserving the RGB? The wording is ambiguous. When I do the Analysis, it says four color plates, CMY and Black (so CMYK). So does that mean it converted the entire document to CMYK?

[vixler]

Update: After deselecting the two options it still shows it is CMYK. So I am wondering when the conversioin took place.