According to the wiki, powered activator rails disable the hopper minecart's ability to pick up items from other hoppers or chests, until the minecart runs over an unpowered activator rail.

This isn't the case, however. The hopper minecart picks up items if the activator rail is powered or not.

How to reproduce:

1. Create a circle track similar to the one in the screenshot. Make sure that both the activator rail and powered rails are powered
2. Put any amount/type of item in the hopper above the rail
3. Send the hopper minecart on its way.
4. Check the hopper underneath the rail for items.

What to expect:

There shouldn't be any items in the lower hopper or the hopper minecart.

What actually happens:

The hopper minecart transports the items from one hopper to the other.