quoted

+- When cloning, the former implies --local option. See
+  linkgit:git-clone[1] for details.
+
+- The latter is implemented using linkgit:git-upload-pack[1], which
+  expects its repository to be a directory, and therefore does not
+  work for bundles (see linkgit:git-bundle[1]).

Hmm, I do not think this is quite true.

If "git clone /path/to/repo.bndl" implied --local, we would end up
trying to hardlink into /path/to/repo.bndl/objects and would fail.

I think what is closer to the reaility is that we check if the
source is a bundle when the local filesystem path is used and try to
clone from the bundle, before using the local filesystem path as a
directory we can "clone --local" from.  On the other hand, when the
<scheme>://<path> syntax is used, we do not even bother seeing if
the named resource is a bundle, or if --local optimization is
possible (because we do not bother seeing if the named resource is a
local filesystem entity, either).

Would the following work better for you?

When cloning, the former will check to see if the source is a bundle.
If it is, it will clone from the bundle, otherwise it will behave as if
given --local. The latter performs neither of these checks, and
therefore does not support bundles.

A possibly interesting tangent to think about is what would happen
if we slightly tweak the above design.  What it would require for
the code to take "git clone https://site/repo.bndl", realize that
the named resource is a bundle file, curl/wget it and clone from
that downloaded bundle?  And if it is feasible to implement, would
it even be a good idea to begin with?  I do not have a ready answer
to either of these questions myself.

I was very surprised to find that cloning from a bundle didn't even work
with a file URL, especially since the documentation seemed to imply that
it should. I assumed that file URLs not supporting bundles was an
oversight, and made some attempt to read the code with a view to fixing
it. Once I realised that file URLs went through a completely different
code path to paths, I decided it was better to just document things as
they were.

I think it would be nice if, at least for file URLs, bundles were
supported. I doubt supporting cloning a bundle over a network would
inherently cause problems (although I'm by no means qualified to make
such an assessment) -- if it's not clear whether it's a good idea to do
so, it could always be implemented without being advertised.