Archives created from an existing install are not cross-OS compatible, no. However if you use the Download Archive option for a product that is not yet installed, or get it via Impulse Anywhere, those will be able to install on any supported version of Windows.
A good number of games can simply be copied directly, then added to Impulse via the Detect Application option and reactivated, but applications or products with (for example) third party protection will have additional dependencies outside their own folders, OS specific components, etc., and this won't work there. It's for these products that the restriction exists (customization apps are a very big part of our business).
