That actually makes the most sense. It makes you queue because there are only so many tests they can administer at a time. So if the website is offline for maintenance it allows those that tried to access the website first to have their spot saved. Rather then forcing everyone to try and get on the website at once when the matinenece window ends. Now I kinda wish more websites that have limited sign ups did this.
If it is for the Government of Cuba then yes. However, individuals can utilize the software.
This is the Bureau of Industry and Security website
This is the law itself