Yup, to emphasize, this is "we want to hire linus torvalds for a specific project" level exception, not "we'll be handing these out to line programmers because comp is higher in that sector" level exception.
You won't be getting one of those unless you're exceptionally well-known enough that an average practitioner in your field would perk up their ears when someone mentions your name as a potential hire.
And really, for the tier of people that would be getting those exceptions, that's still not a great rate of pay and they'd still be taking huge paycuts to work for the government. Like ok, we can get $300k a year for Linus but... he can walk into fifty companies and drop off a resume, cold, asking for triple that and get offers before he's back to his desk.
I only worked with one computer scientist in an ST role during my two years at USDS. He was an ACM Fellow and had a PhD from MIT, so it's not something anyone should expect to get just because they had "senior" in their title at a FAANG.
Contractors don't have the same statutory caps on how much an individual role can pay, but salaries are part of contract bids, and a bid can be rejected if an individual salary is too high.