All of your customers will continue to be Facebook users if you post things on a Facebook page that only Facebook users can view. And Facebook users are an apparently diminishing portion of the population, as per the article this thread is discussing...

Not a good plan for any business, I would think. Would be nice to see more businesses on Mastodon or (gasp!) just run their own websites again. Can you imagine how difficult it must be for a business to buy a domain, hosting, and slap together a static site in this day and age?