There are no homogenieties at the interface.

Problems caused by wetting agents might include changes in refractive index or changes in silver type or grain size or coupler (in color), or combinations.

As I said, you have everything just about right.

In the photos on the left there is a 10 layer color film coated at high speed in one pass. The irregularities in the layers are due to the microtoming and mounting. You can see that there are no intermixed layers in the processed sample on the right. (used with the permission of Bruce Kahn) I have seen others without the 'ripple' but I have none of those. I will look and see if I can find some. The ripple, if real, would mess up the image really badly, so I hope you can understand that this is an artifact.

In the photo on the right, is a 5 layer structure coated one pass at a time. This is a dye bleach (Ilfocolor) prototype I coated and again you can see no interlayer mixing.