For those of our friends who do not know, Facebook earlier allowed the add to cart checkbox to be pre-checked for anyone adding something to cart. That allowed for huge opt-in rates but ended up compromising the end-user experience resulting in high block rates. This was removed by Facebook on April 9th, 2019 to preserve the user experience. 

Interestingly, we launched BiteSpeed only after the pre-checked checkbox was removed. We saw that merchants relied on the pre-checked checkbox heavily and were now getting poor opt-in rates. The solutions that still performed fine, relied heavily on integrations with third-party opt-in tools. 

So our approach is to provide the highest converting opt-in tools like our Spin The Wheel Popup, built-in with our messenger marketing product to ensure merchants can enjoy a high opt-in rate and continue leveraging the benefits of messenger marketing.
Feel free to have a look at this overview of our opt-in tools.