I actually thought of what you suggest. But:
1. Testing plain http may never reveal things like this (which may be
additional info)
2. Testing plain http may not show connections specific to TLS (e.g. OCSP
requests), so it may create a false sense of privacy
3. Although for the sake of testing we may create a simplified connection
test access by IP address already goes a bit too far from what normally one
does in a browser. So it may limit the scope of what we would actually see.
Additionally it may hide some irregular connections related to name resolving
(if there are any).
A full featured test would probably look at many various aspects separately
and in combination. However this one is really simplified, not an extensive
one.
BTW you can test for yourself too and share your findings. You may even find
a better and more complete testing procedure. It seems everyone is waiting
for me to test and saying "how nice" :)
