Module available but not reported as installed - powershell

Question

Using PowerShell (version 5.1.17134.228), found some unexpected differences between Get-Module and Get-InstalledModule, in that some modules that I'd expect to be returned by Get-InstalledModule are not.
As an example:
Get-Module -ListAvailable -Name 'Hyper-V'
Get-InstalledModule -Name 'Hyper-V'
Output:
PS C:\> Get-Module -ListAvailable -Name 'Hyper-V'
Directory: C:\WINDOWS\system32\WindowsPowerShell\v1.0\Modules
ModuleType Version Name ExportedCommands
---------- ------- ---- ----------------
Binary 2.0.0.0 Hyper-V {Add-VMAssignableDevice, Add-VMDvdDrive, Add-VMFibreChannelHba, Add-VMGpuPartitionAdapter...}
Binary 1.1 Hyper-V {Add-VMDvdDrive, Add-VMFibreChannelHba, Add-VMHardDiskDrive, Add-VMMigrationNetwork...}
PS C:\> Get-InstalledModule -Name 'Hyper-V'
PackageManagement\Get-Package : No match was found for the specified search
criteria and module names 'Hyper-V'.
At C:\Program Files\WindowsPowerShell\Modules\PowerShellGet\1.6.5\PSModule.psm1:9125 char:9
+ PackageManagement\Get-Package #PSBoundParameters | Microsoft. ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : ObjectNotFound: (Microsoft.Power...lets.GetPackage:GetPackage) [Get-Package], Exception
+ FullyQualifiedErrorId : NoMatchFound,Microsoft.PowerShell.PackageManagement.Cmdlets.GetPackage
As you can see, the Get-Module command is returning a local path of the Hyper-V modules, so it's definitely installed locally, but Get-InstalledModule cannot find the module.
Is this a bug or have I misunderstood what Get-InstalledModule is meant to do?