I had the same results, and noticed that, at least for me, AD consistently only imports 68 swatches per palette using this method. The workaround I used was to take multiple screenshots in Photoshop's swatches panel of the Google palettes you referenced, then named them sequentially, e.g., "Google Material Expanded Palette 1", "Google Material Expanded Palette 2", etc and imported them individually. That seemed to allow me to capture more of the colors, but the downside is they are spread across multiple palettes in AD.