Earlier quoted context omitted.
Comp clawbacks are quite common in finance, at least contractually. It's rare for it to go ahead, but it happens. It isn't some especially weird thing.
What is the structure of those compensations, and the mechanism for the clawbacks? Equity is taxed when it becomes the full, unrestricted property of the employee, so depending on the structure these threatened clawbacks could have either (1) been very illegal [essentially theft], or (2) could have had drastic and very bad tax consequences for all employees, current and former. I'm not surprised that they're rapidly…
I guess these agreements mean that the property isn't full unrestricted property of the employee... and therefore income tax isn't payable when they vest.
The tax isn't avoided - it would just be paid when you sell the shares instead - which for most people would be a worse deal because you'll probably sell them at a higher price than the vest price.