The object info node output an instance as a performance optimization.
Before that optimization was (almost) invisible to the user, but now that
we aren't automatically realizing instances, it isn't intuitive for a
single object to become an instance.

I refactored the transform node so its ability to translate/transform an
entire geometry set was more usable from elsewhere and exposed the
function to get a geometry set from an object.

Another approach would be removing this option and adding a "To Instance"
node that could create an instance from regular geometry. That solution is
more flexible and avoids some nasty workarounds needed to choose
between multiple real geometries in the instance on points node.

There was discussion of adding this same option to the collection info
node. However, currently I think that there isn't the same expectation that
the output of the collection node is not an instance (because a collection
is just a container for multiple objects!), so I actually think it's more intuitive
to just use the realize instance node in that case.