It is very explicitly and obviously against their terms of service if you run a whois from a cli. The first lines returned: "You are not authorized to access or query our Whois database through the use of electronic processes that are high-volume and automated except as reasonably necessary to register domain names or modify existing registrations."

Perhaps you can argue against the effectiveness of their countermeasures, but from an legal standpoint, they do not authorize that activity. I take that to mean that they probably implement some technical countermeasures, but I cannot speak to their level of sophistication.