Rotten flesh and rotten flesh block are still compostable in version 2.1.0; this wasn't fixed when the rest of the items affected by #74 were made un-compostable. Making vanilla items compostable when they aren't in vanilla is arguably out of scope for a mod focused on building blocks, and would be better suited for a vanilla tweaks style mod. The rotten flesh block I realise is not a vanilla item, but it wouldn't make sense for it to be compostable when the item isn't.