It sounds like that's exactly the concern that motivated Twitter to have this policy. Some politicians are using Twitter in ways that would get normal users ban

It sounds like that's exactly the concern that motivated Twitter to have this policy. Some politicians are using Twitter in ways that would get normal users banned. But there's a public interest in letting them say what they're going to say. So Twitter lets them stay on the platform, and this policy is about minimizing the fallout damage from that.