Why do women's 800s so regularly positive split?

look at men's races and you might figure out why

800’s are usually and ideally run with a positive split. Take Rudisha’s world record—49/51.

The men’s 800 at USAs was an incredibly tactical race, those guys are used to going out in 50/51, so they were bound to close hard and negative split off of a 54 opening lap. The women’s race was a far more honest pace, perhaps a bit too fast but certainly run in the ideal positive split manner.

No matter how slow the pace first 400m, unlikely that one will sprint into a wall of pain, sub-50 seconds, second 400m. Eg. 2014 African Championships, men 800m final: 1) Nijel Amos, BOT, 2) Mohammed Aman, ETH, 3) Taoufik Makhlkloufi, ALG & 4) Ferguson C. Rotich, KEN. They passed first 400m, 57.xx. I do not think any of the four men stated broke 51 seconds, second 400m.

David Rudisha World record was ran in a positive split.

The only time a world class 800m runner does not positive split is in a slow race.

So the answer to your question is that women regularly run pretty fast in their 800m races.