Rule of thumb for free services. If you are using a free service, you are not the customer, you are the product.
I agree, but I think it is just promotional towards folks using their email service. I have a free Proton email account and it is great. But of course they would rather have me sign up for premium. But like the article states, the VPN service is limited and you have to upgrade if you want better. So it is a “draw” item. A promotional sample...