Tracking cart update and removal

Hello Ppiwik community,

Piwik user docs states:
“Every time a visitor adds (or updates, deletes) an item from his/her cart, you can use Piwik to track the latest cart subtotal as well as products left in the cart.

To track Shopping Carts with Piwik, you would call the javascript function trackEcommerceCartUpdate() every time a user is adding, updating or deleting a product from the cart.”

When looking in piwik.js code, “products left in the cart” seem to be stored in Tracker’s ecommerceItems, which can only be updated by addEcommerceItem calls.
For cart item quantity update events, it seems addEcommerceItem should work, just passing different quantity using same SKU which got added before.
Problem is, I do not see support for removal of cart item event, unless updating quantity to 0 is considered as removal by piwik backend.
piwik.js seems to keep items with quantity 0 and sends them in tracking request content.

Are these assumptions about how to track, with Piwik, update and removal of cart items correct? If so, please consider updating user docs.

Kind regards,
Stevo Slavic.