I'm confused by some frozen vegetables packaging saying they need to be fully cooked. i thought frozen are just as safe as any other vegetables?

Legal statement: They are just as safe but fresh vegetables can be contaminated too (I.e. Recent salmonella outbreaks)

Half cooked: these vegetable are not fully cooked and before consumption needs full cooking. They may be safe but still uncooked

Not a matter of safe: I don't think it is a matter of safety but rather they are making the point that these frozen veggies are not cooked and you need to cook them just like you would raw veggies.

Safe vs tasty: It's not a question of safety but of taste. You could safely eat the frozen vegetables after letting them defrost without cooking them. But they wouldn't taste good that way.