But it is strange that Webflow would allow a configuration that is guaranteed to break your site.
I can definitely understand why this may seem strange in this particular instance, however this configuration does not always break a site. It only does if your DNS provider doesn’t offer CNAME flattening.
If you have a DNS provider that does allow for CNAME flattening, then the root domain will work perfectly with SSL hosting.
This is not a limitation of Webflow, but of DNS providers. Some do offer CNAME flattening, but most do not. The benefit of CNAME flattening is purely aesthetic — that is, if you want your site to appear as site.com vs www.site.com.