The aggregate of your interaction with sponsored content is sent to Mozilla (sponsored links you've seen, clicked on, and how many times you've clicked on them). Your browsing history is never sent, either in whole or aggregate. It also sends your region, country, state, and county, but not your IP or anything that could uniquely identify you.

Since you aren't being identified, nor can you likely be identified, it's privacy respecting. Other advertisers attempt to build a uniquely identifying profile on you where they grab as much information as they can. When compared, Pocket looks a lot better than every other advertiser.

Regardless, I'm not comfortable with Pocket, so I disable it. I can't disable advertisers tracking me.