I made a little spot for my sniffers and covered the ground in moss using bone meal. Then, I broke the azaleas and the grass until there was just moss and moss carpets. I waited for them to find ancient seeds but it felt way slower than when the ground was grass, so I remebered to see the f3 overlay, where it shows if a sniffer can dig into a certain block with "#minecraft:sniffer_diggable_block". By doing that, i found out that moss is a "diggable block", but that its carpet variant wasn't. I removed the carpets and they started finding seeds much faster.