This is not multi-cloud as it is commonly defined: Simultaneously handle workloads with multiple cloud vendors, to prevent lock-in to a single vendor. Rather, this is passing workloads between AWS and Google to leverage the advantages of each. A useful strategy, but the title is a bit misleading as it goes against the colloquial definition of multi-cloud.
I know you can use multi-cloud to prevent lock in, but I've never heard the term used to strictly mean that. Almost everyone I work with uses the term multi-cloud as "workloads on multiple cloud vendors."