I think it's not just about proving a claim. The same argument that in a democracy, you should build checks and balances to avoid sleepwalking into a dictatorship, is valid for companies, especially internet companies. Look at Google, Apple, Microsoft, Facebook and friends. Cloudflare plays nice because it wants to frictionlessly slide into a position where it can extract rent. Today, they are powerful but are not there yet. They're easy to migrate out of because their offerings, amazing as they are, are not irreplaceable so people cannot yet be made hostages. Mostly what happens is your customers feel like CF is holding you for ransom without you knowing it.

When they start charging per packet and making you money, you will become as dependent on them as Apple developers are on Apple, and you'll find out how nice they are.

I have the same fear of tailscale. They are so amazing I just want to move every piece of my infra to them, business and personal, my family's devices, everything. But over time I've gained this instinctive distrust for low friction from startups, especially when the effect (intended or not) is you forgetting how to manage your own tech.