ABS can sometimes be molded with no draft angle, and your thin wall at the top can certainly be done.
However, whether or not your Chinese supplier can do it depends on the type of molding press they are using, whether they have optimized the mold construction, and whether they can achieve optimal process conditions.
There’s a reason why Protomold and the pens you observed have less draft and thinner walls.
It’s because they’re not molding in China.
Those Chinese kids are fast and they work hard, but they’re not using the best tools and equipment.
My experience is you’ll need to allow them the widest processing window possible, and that means maximize draft and make your walls at least .060" thick.