The short answer is yes. The federation server fully qualified domain name (FQDN) is the same for internal and external users. Internal users need to resolve the name to the internal AD FS server, whereas the external users need to be redirected to the external facing WAP servers. While there are methods to provide name resolution, for example adding a host record, split DNS is usually the recommended approach.
VN:F [1.9.22_1171]Will I need to have split DNS (same DNS namespace internally and externally?),