Speaking as a VC who interviews for our own entry-level roles, I don’t think your current pitch will necessarily hurt you, but it won’t really help you stand out either for these reasons:
Not a unique pitch: It’s actually the opposite of nonconventional to offer to work for free because the bar for making this offer is low. Many people can and do offer to work hard for free because you don’t need experience or any other value to be able to offer this.
