Let's say this startup subsequently adds a new line of services / products under another fruit name. Likewise Apple doesn't object because it has zero confusion

Let's say this startup subsequently adds a new line of services / products under another fruit name. Likewise Apple doesn't object because it has zero confusion with Apple. Perhaps they acquire BlackBerry now to add another fruit theme to their lineup. Now they want to add an Apple-themed subbrand as well, and when Apple objects, they have to fight it out because the company is just trying to complete its fruit branding and Apple didn't previously object while it was building out the fruit branding. Yes, it's a stretch but likely by registering its objecting to the trademark application (with the USPTO granting this trademark anyway), Apple can ensure that down the road there is no risk of the company (or any other company) being able to justify entering Apple's trademark turf.