Unfortunately, there is not much we can do about transfer-encoding, but the data is otherwise exactly as is returned from the browser. Browsertrix uses the browser to create web archives, so users get an accurate representation of what they see in their browser, which is generally what people want from archives.

We do the best we can with a limited standard that is difficult to modify. Archiving is always lossy, we try to reduce that as much as possible, but there are limits. People create web archives because they care about not losing their stuff online, not because they need an accurate record of transfer-encoding property in an HTTP connection. If storing the transfer-encoding is the most important thing, then yes, there are better tools for that.