In a hot market, your best chance of career progression and maximizing your compensation is to swap jobs every 2 years or so. Visa holders have a much harder time doing this.

Additionally, there are additional burdens on the employer to hire visa holders. For a large company, this process is solved. You have lawyers on retainer. You have a pipeline for the paperwork. It's a non-issue. But an early stage startup? That's a lot less likely. So visa holders are, by definition, more limited in their job opportunities.

Even if you can job hop, if your ultimate goal is to get a green card, you have a problem. Will your new employer sponsor your green card? How long will it take? Or are you better off waiting for your current process to go through? Best case, this whole thing takes just under a year. But it can take years completely randomly and there's nothing you can do about it (eg you get randomly audited).

And if you were born in one of the four high-demand countries (India, China, Mexico, the Phillipines) you have an even longer wait.

Also, after you get to 6 years on your H1B you really can't swap jobs anymore. You just have to wait for your green card at that point.

Now that's not strictly true. There are self-sponsor options for both visas and green cards but the bar for these is much higher and you'll need to hire your own lawyer for this.

So there's no directive on treating visa holders differently but bias creeps into the process. Why push someone for higher bonuses, more RSUs or promotions when they can't leave but another one of your "stars" can leave? This may not be conscious either. And it may happen on a level above you, as a manager, because your director is ultimately responsible for balancing out ratings and promotions across their org.