1) As you state, most high salary positions don't publish their salaries publicly, so a website with developer submitted salaries like levels.fyi provides better user metrics.
2) Most of the results on the "top ruby" link [1] are from dice.com... which then links to another job board [2], jobot.com. The post from jobot.com appears to be from a contingency recruiter with no company name stated. The lack of transparency there is a bit unsettling, but it might be accurate??
3) The only post in the top 20 that is actually from the hiring company is for a "contract" position, where the "salary" is the contractor hourly rate annualized, ie: doesn't cover health insurance, self-employment taxes, etc... so that "salary" would be much less apples-to-apples with a full-time position.
[1] https://www.devjobsscanner.com/top-paid-ruby-jobs/
[2] https://www.dice.com/jobs/detail/dc2e0bbd9bdcad4ac553c88fb06...