Yes, that is correct if you are using Skype for Business Online. When you create a meeting request in Outlook you just get the “Join Skype Meeting” message.
This is because dial-in meetings are an add on to Skype for Business Online and the PSTN Conferencing feature is needed. As long as you are an Office 365 global admin (or billing admin) and have users with the Skype for Business Plan 2 licence you can add this subscription by clicking this link: https://portal.office.com/SubscriptionDetails?OfferId=A9643248-CF41-4F8B-A29F-507EB6EFAC3E&adminportal=0
Once subscribed and the licence added to the relevant users, those users will get a phone number in their Skype for Business meeting – see more here.
Tolled dial-in conferencing and domestic dial-out conferencing services are both included in the PSTN Conferencing service plan. Although there are no distinct service limits associated with tolled dial-in and domestic dial-out conferencing, Microsoft monitors the service for fraud or abuse and reserves the right to limit use in cases where the service quality might be compromised.
Beginning December 1, 2015, there is an introductory offer period during which international dial-out capabilities are available to customers in all PSTN Conferencing sell-to countries. These customers can use international dial-out conferencing to any tolled number residing in any one of the PSTN Conferencing sell-to countries.
When consumption billing is enabled, toll-free dial-in service will also be enabled.