There's several factors that make this irrelevant.

1) YC's incentives look very different from VC's: they get common shares, not preferred. This means their incentives are more aligned with the founders than with future investors (for example, if a VC has a controlling stake in the company & wants to fire the founder and dilute the common shares to basically nothing, then YC gets similarly diluted).

2) The dilution effect of the option pool on YC's shares is trumped by the dilution effect of future investments on YC's shares. If expanding the option pool has a marginal dilution affect but dramatically increases the likelihood of success, then that's a no-brainer for YC to push for.

3) YC's business model is dominated by the extreme outlier successes (e.g. Dropbox, AirBnb). Thus, YC does better by doing these three things better:

A. Increasing the likelihood that future successes are funded by YC (i.e. the founding team chooses YC early on)

B. Increasing the probability that a startup will become an outlier success.

C. Given that a startup is becoming an outlier success, multiply that success to the extent possible.

This piece hits nicely at each of those points. For A, YC takes a leadership role in how to structure a cap table, making founders look more to YC. Also, YC startup employees (ie future YC founders) think better of YC. For B and C, once a company grows beyond the founders, each employee makes very meaningful decisions on a daily basis that impact both the company's likelihood of success and magnitude of success. Aligning these employee's motivations with the company's further helps make these decisions better for the company.

It's about as meta-strategy as you get. It doesn't just make YC look good for advocating better incentives to attract better employees, it makes YC look like a leader. And makes them look extremely smart for seeing the way to look like a leader.