Configuration - ACME cluster url


As complete newbie within Vault, perhaps I should have read even more than I did, but in the ACME guidelines of Vault it states a requirement of a cluster endpoint which is of course needed for ACME.
But why the naming convention of cluster?
Is it simply because Vault is usually deployed in clusters?

As someone who seeks simply to deploy it my my single homelab, as a single instance it got my setup spider senses tingling that there might be some cluster configuration/overheads I am not seeing.