Should restricted stock comp be considered deferrable income?

I think the way equity comp at private companies works is both absurd and a totally logical response to the tax code. At a basic level, companies want to align incentives and also to be able to make attractive comp packages, while controlling burn. But as https://www.benkuhn.net/options eloquently explains, this creates a minefield for employees to explore, which undermines the use of equity as an incentive. Either you disregard it or you waste a lot of mental energy trying to optimize your strategy.

It seems to me that this problem would be solved if stock comp simply counted as capital gain at the time of sale. That way, employees wouldn't be penalized for receiving illiquid assets. Is there a major downside to this?