I don't think Reiner lied or made stuff up. Some devs told him that PS5 is (was?) more powerful.
Without knowing anything more than that, even Reiner himself, can't really say (or did he). He simply relayed what some devs told him. Nor do we know anything about the devs who supposedly relayed this information. Are they the technical types (engine designer, programmer, etc) or more on the other side of development (artists, marketing). Dev can be a very broad term. Without knowing who made the statement that PS5 is more powerful and based on what criteria, we shouldn't treat this as gospel, but just another data point until the specs are revealed.