We are working with your plugin and I believe you need a "Passive Opt-In" option.
The reason is there are many form functions that cannot work with Active Opt-In (relying on delayed clicking a link in an email for fore the otherwise instant actions of the form can be completed).
Passive Opt-In simply means the same functionality, that the email submitted is subscribed as confirmed immediately but you enforce that all users of that option send an email that has a visible Unsubscribe link in it - which all emails should have anyway!
This make development faster and easier, it makes subscribing faster and easier for the vast majority of legitimate subscribers - and there is already a double-opt-out method of subscription removal through the time period with no email clicks where users are unsubscribed for not being engaged.
This helps us, yourselves and users increase subscriptions, which is good for all of us and has no down-sides.
Your current restrictions are unnecessarily overbearing and discouraging for the vast majority of legitimate uses and my passive opt-in suggestion solves all of this.
Please escalate this ticket to decisions makers that will give this serious consideration, we are a 20 year experienced developer team and this is qualified experienced user feedback to help everyone very easily with this simple change or addition to your existing otherwise good product and services.
Many thanks,
Marcus