The new ability to set up Public Facing Forms is an awesome new capability that has been added to Form Designer.
Note that this function is available only for Office 365 customers at this time.
As with many new features, this might have flown under the radar for some users.
In short, the added ability is a big deal!
I have had many customers ask about doing public facing forms in SharePoint over the years. It is a common need.
In general this hasn't been possible in SharePoint. In fact in recent years, you can't have any public facing content in SharePoint Online.
Without Ultimate Forms, the opportunity to do this kind of thing isn't very good. I would probably tell a customer to use Microsoft Forms which is a very simplified form building tool similar to Google Forms. At first it is easy to create a form with those tools, but in these cases there are very few customization options and very few options for integration into other systems.
You might have to build some kind of custom Power Automate script to route the responses to SharePoint creating extra work and maintenance.
When learning about new functionality, I really do best by testing out the functionality with a simple example.
We've added a very easy to follow step-by-step on setting up a custom Contact Form which you could use on a public facing web site.
After doing this practice exercise, you are sure to realize lots of possibilities to gather information from customers and use that data to automate related processes.