Learnable Downsampling : Downsampling to 1/4 size

[tadbeer]

Which feature map is grid-pooled when being downsampled to 1/4 of the original image size? As the shallow encoder's output features are the ones given to grid-pooling function; and those features are already of 1/4 size of the original image. Then grid-pooling them to 1/4 size wouldn't make sense, unlike when using them for downsampling to 1/8 and 1/16 size. Is a different feature map other than shallow encoder's output is used in the case of 1/4?