This seems to be the case so far. I hope it scales. Lemmy servers actually have an incentive to eliminate those things - they drive up server costs and could lead to defederation. Plus, they are usually running a server for the sake of enjoying giving people a place to socialize.
Ever tried getting an obvious bot/spam account banned from Meta? Good luck! Those accounts are generating ad impressions, so who cares if they're fake? Meta could invest the profits generated in 2 minutes and fix the problem for good, but their incentive is to keep the problem just below the threshold that people leave the platform.