Surely there has to be another way to do this besides logging in with Twitter. Heck, they could just have you post a verification tween on your Twitter account.
You can't view an account's followers/following without being logged in. And if you try to back a service using a single bot account, you're going to get instantly banned b/c of suspicious traffic.
Keybase somehow manages to do verification through a twitter post, surely there could be a similar method for Mastodon?
You can see a person's latest tweets without a login. Just play around in incognito and you can see: https://twitter.com/elonmusk
Maybe they can create a specific pattern people can enter in their Twitter bio, then build a crawler