I would expect when on FreeBSD for $IsLinux to be false

I would expect $IsLinux to have the same value as [System.OperatingSystem]::IsLinux()

PS> @{ IsWindows=$IsWindows;IsLinux=$IsLinux;IsMacOS=$IsMacOS }

Name                           Value
----                           -----
IsLinux                        True
IsMacOS                        False
IsWindows                      False

PS> [System.OperatingSystem]::IsLinux()
False
PS> [System.OperatingSystem]::IsFreeBSD()
True

no actual error