If you don't want to do that you don't have to, as far as I understand (and if I am wrong here, that is what I think would be particularly fascinating); you can instead use the (existing) WhatsApp Business API "client"--which you would have to host yourself, coming up with your own mechanism for sharing access to it within your organization, and handling your own security and durability measures for the keys involved--rather than using the (as yet unreleased) Facebook hosted client feature they want to role out for the large number of businesses that probably don't want to deal with all of that. As far as I understand (and I would be fascinated to learn I was wrong here), using the API client means your communications with your customers would be end-to-end encrypted.

Here is the (afaik, prior) documentation for the (afaik, secure) feature that they are seemingly having a hard time getting people to adopt:

https://developers.facebook.com/docs/whatsapp/getting-starte...