First, how is it anti-trust? And second, it's been shown that faster page loads = better conversions since your bounce rate drops. This is especially true for mobile.
Why would you use an AMP page for that? It was specifically NOT designed for those use cases.
Now back on your point: if the users who have a question are a small % of the total users, why would you have all users load the heavy chat window on mobile devices with limited screen space?