The Bug:
Despite being a "sniffer_diggable" block in the code, Sniffers will never dig in normal mud blocks. They will dig in muddy mangrove roots, but despite searching and sniffing on mud blocks, they will never actually dig for seeds.
I suspect this may be because the mud block isn't technically a full block; you sink down a bit in it. This may mess up something with the Sniffer's block detection. Muddy Mangrove Roots, for comparison, are a normal full sized block.
This behavior can be observed here:
[media]Steps to Reproduce:
Spawn many Sniffers on multiple platforms of "sniffer_diggable" blocks, including normal Mud
Wait for them to dig for seeds
Take note of how all will, except for those on normal Mud Blocks.
Orbic
v-hjonson+bugs
This is still an issue on Java 1.20 / 1.20.1 as of today's date (06/23/23) – Sniffers will never dig into mud. Mud being the only diggable block whose height allows for hoppers underneath to collect dug-up seeds, this issue is a major obstacle to seed farming.