This is a part of their sales playbook. Even if you have a top of the line modem that just came out and is on their support list, they will tell you its either

This is a part of their sales playbook. Even if you have a top of the line modem that just came out and is on their support list, they will tell you its either unsupported or about to become unsupported and push you to rent garbage from them instead. You can never trust anything a phone/chat rep tells you because they're aggressively pushed by management to integrate sales into support.