To support the Windows Sandbox and WSL2, Hyper-V has been split up
into two parts in Windows 10.
The hypervisor, known as the "Virtual Machine Platform", is available
on all Windows versions and is the minimum that is required to run the
Windows Sandbox and WSL2 as light-weight virtual machines that are
tightly integrated with the host.
Hyper-V Manager is now a distinct Windows feature that is used for running
full-featured virtual machines whose integration with the host is
limited. It is not available on Windows Home.
Answer : The Windows Sandbox does require the underlying base of
Hyper-V, whose feature is called "Virtual Machine Platform", but does
not require the heavier upper part of Hyper-V, whose feature is called
"Windows Hypervisor Platform".
Read also :
Windows Sandbox No Hypervisor Found Error: Solution.
I have today found this excellent summary in the article
What’s the difference between Hyper-V, Virtual Machine Platform, Windows Hypervisor Platform
that explains the involved Windows components in the order of
top to bottom:
“Hyper-V” is the component that adds the management tools and platform
to create and run virtual machines on Windows 11.
“Windows Hypervisor Platform” enables the user-mode API components to
allow third-party virtualization stacks and applications (Docker,
VirtualBox, and QEMU) to connect and interact with Hyper-V.
“Virtual Machine Platform” is the component that enables
virtualization support to run virtual machines, and you must turn on
this feature to use the Windows Subsystem for Linux (WSL). In
addition, the component can also help to create MSIX app packages for
an MSI or App-V.
In other words, if you want to create virtual machines on Windows 11,
you want to enable the Hyper-V option, and if you plan to set up WSL
on your computer, you want to install the Virtual Machine Platform.
A remark by user71659 adds this information :
It's split into multiple pieces now.
The hypervisor is installed by default in order to support features like Virtualization-based Security, which is automatically enabled on adequately new machines/installs.
This explains why Windows Sandbox does not need the
"Virtual Machine Platform" feature in order to function.
In all, virtualization in Windows 10/11 has now been divided
among four levels of functionality.