Changing policy, Y Combinator cuts its pro rata stake and makes investments case-by-case

In a message posted to its internal communications channel earlier this week, the massive startup accelerator Y Combinator said it will change the terms of its own PPP (the YC pro rata investment program) and investing in companies raising seed and Series A rounds on a case-by-case basis.
The company began a policy of investing in every seed and Series A round for its portfolio companies back in 2015.
Since then, it has taken a 7% stake in every company that raised a priced seed and Series A rou