How to get Chrome to show bytes or time remaining for content-encoded downloads

Question

I'm writing an HTTP application that serves large files, and I would like web browser to show an estimate of time and/or bytes remaining. However, I would also like to use gzipped content-encoding, since the files are quite compressible, but would also like the browser to automatically decompress the download so the user doesn't have an extra step to do this manually.

However, it seems as though Chrome (101.0.4951.64) won't show an estimate of time remaining for gzipped content-encoded downloads. The below simple HTTP server

from http.server import HTTPServer, BaseHTTPRequestHandler
import time
import zlib

class SlowHandler(BaseHTTPRequestHandler):
    def do_GET(self):
        self.send_response(200)
        self.send_header('content-disposition', 'attachment; filename="my.file"')
        self.send_header('content-length', '1000000000')
        self.send_header('content-encoding', 'gzip') # If commented out, Chrome shows time remaining
        self.end_headers()

        obj = zlib.compressobj(wbits=31)
        compressed = obj.compress(b'Some data to compress. Some more' * 10000)
        self.wfile.write(compressed)
        self.wfile.write(obj.flush()[:-1])
        self.wfile.flush()
        time.sleep(10)

httpd = HTTPServer(("0.0.0.0", 8006), SlowHandler)
httpd.serve_forever()

results in this if I go to http://localhost:8006

But if I don't send the content-encoding header by commenting out that line, then it does show an estimate of time remaining:

When testing in Safari, even with the content-encoding header, it seems to always show an estimate of what's remaining:

Is there a way to get Chrome to show such estimates even for content-encoded downloads?

Edit: in case this is a bug, have reported it at https://bugs.chromium.org/p/chromium/issues/detail?id=1329738