You're seeing some responses to this that are very cultural. Personally, I don't think a slow coast is a good long-term strategy for most people under a lot of circumstances (for many reasons). But putting the least effort in is seen as pretty normal in a lot of cultures. As someone else said, you're seeing a lot of Calvinist moralizing here IMO.
That “million people would kill for a chance” to be at a FAANG is not the employee’s problem anymore. The moment the company extended the job offer already created “a million” job applicants who didn’t get an offer. Behaving in a way that suggests continually begging “to stay in” just to get to create the net gains for other people, the investors and top management, deserves a therapy session on personal self-worth, which is a personal problem not a business matter.
Now, as for the matter of personally going above and beyond, that’s actually a separate matter - no need for emotional entanglement of the the business reality and personal reality. If the employee wishes, as they’ve expressed, to go above what is satisfying the business (given they’ve reported no management has complained) then by all means, find more work with outside teams within the company, tactfully speak to the manager about the concern, or just leave and start a new job or venture.
The moral guilt argument over the transactional relationship between an employee and the business, though, is at best naive, and at worse unevenly extracting more energy from the employee than the business. If the company has continued to pay the employee without complain, that’s their own moral dilemma for allowing it.