Browsers don't agree on mutation records for .append(documentFragment) #1509

What is the issue with the DOM Standard?

I'm not sure how much flexibility implementations are meant to have regarding emitting different mutation records, but basically the following code has different results in Chrome/Firefox compared to Webkit (tested on Epiphany):

const parent = document.createElement("div");
const fragment = new DocumentFragment();
fragment.append(document.createElement("foo"), document.createElement("bar"));

const observer = new MutationObserver(console.log);
observer.observe(fragment, { childList: true });

parent.append(fragment);
    
console.log(observer.takeRecords());

In Chrome/Firefox this prints a single mutation record with both elements in removedNodes, but in Webkit this produces two mutation records with removedNodes containing a single element in each record.

Is this something implementations should align on? Or are implementations expected to have flexibility with regards to the exact batching of their mutation records. (I noticed this because I'm implementing a pure JS implementation of just the DOM spec + the HTML parsing methods, and noticed these records didn't match all browsers).