Polaroid B&W materials depend on development in an environment high in silver halide solvent, so that the positive image is formed from the salts dissolved as leftover from the negative image. These are depositied on nuclei in the reciever sheet from the donor sheet (the original exposed negative).
Imbalance results in loss of speed and tone scale.
So, with balance, you get both a positive and a negative. The positive is what we generally want, but sometimes we want both. Polaroid has offered products that do both.
In any event, the dissolved silver halide (positive) migrates to the reciever sheet and precipitates out to form a positive image by reduction and we have both a negative and a print.
This is B&W silver only.
In color, the color dyes are hydroquinone containing azo dyes. They dye that developes silver becomes a quinone and is insoluable. The remainder (positive) is soluable and migrates to a mordant sheet. This forms a positive image.
Neither method was in the capability of Land, so Kodak made the original materials, but they were made under strict secrecy according to agreements between companies.
The result is that I know little about the materials due to that secrecy. Kodak would not let employess know what was done between companies.