It probably depends on the way each one of us sees the use of links and property mappings, but to me that difference you point out "looks" logical.
The ExtensionData property is a property, that was added by the PowerCLI Dev team, to have quick access to the underlying vSphere object.
On top of that they introduced some serious performance gains by only fetching what you actually access.
The ServiceInstance.Content.Setting property is a property that is present in the vSphere ServiceInstance object (nothing to do with PowerCLI) and that actually contains a MoRef to another object. To simplify I consider a MoRef as a kind of pointer.
To get the object a MoRef 'points' you have to use the Get-View cmdlet.
So this
(Get-View $global:DefaultVIServer.ExtensionData.Content.Setting).Setting
looks quite natural to me.
There is a way to access the OptionManager object in a sort of way like you suggest.
It involves the use of the UpdateViewData method and the LinkedView property.
$si=$global:DefaultVIServer.ExtensionData
$si.UpdateViewData("Content.Setting.*")
$si.Content.LinkedView.Setting
There is some info on this method in Optimize the performance of PowerCLI’s views.
But while this might look rather intuitive to a developer, I personally think this is way beyond what a vSphere administrator sees as "natural" Image may be NSFW.
Clik here to view.