The downside is, old beaky is going to be a prime target for removal, as until you've used its ability to convert the exiled cards into life gain, they have a chance to extract them from its stomach
But in hindsight, its hard to argue that those desperate measures worked, and the companions have settled into a more sustainable role across most formats
They interact with the graveyard immediately
If there's a cost associated with having that creature block, its controller isn't forced to pay that cost, so it doesn't have to block in that case either
Ill demonstrate. Illustrated by Titus Lunter Standard Not Legal Alchemy Not Legal Pioneer Not Legal Historic Not Legal Modern Not Legal Brawl Not Legal Legacy Not Legal Comp
Both of those tools also have other things they give to my deck