SEO establishes discoverability. GEO improves the clarity, structure and authority of the information generative systems may retrieve and use.
The distinction that matters is the unit of interest. Search engines rank pages against a query. Generative systems assemble an answer about a subject, and where that subject is your organisation, they need to establish what it is, what it does, who it serves and whether its claims can be relied upon.
Many websites are perfectly adequate for the first task and quite poor at the second. A page can rank well for a service term while never stating, in a form anything could extract, which organisation provides that service or what distinguishes it.