OrioleDB isn't a separation of storage and compute, its a more efficient storage engine for Postgres to replace the existing HEAP engine. This is like how in MySQL we could swap MyISAM for InnoDB and eventually RocksDB.
I did some benchmarks on it previously to show how much of an improvement it gives over the stock HEAP engine
EDIT: correct link to the public dashboard below, thanks for the heads up @kiwicopple