Resolution steps

1. Converted primary user account from a microsoft online services authentication to a standard local user account. As-is account is already part of local administrator group, as is new account when it's converted)

2. Run the installer as Administrator (right click, select) and it installed perfectly.

In a nutshell, when you go through the initial unboxing and OS setup for this machine, it has a new setup process that is mainlined as an online registration and integration with Microsoft services. Therefore, you're really *encouraged* to use a Microsoft-enabled email address as your primary login. The user name the you create is using these credentials to authenticate against your machine.

It used to be that you just typed in Dave (or whatever name you wanted), and it created a local user account and put it in the Local Administrator group for the machine. This change means that you're no longer using explicit OS-level security, anmd my suspicion is that it creates a unique type of local user account that is treated differently by default. It may be part of the local admin group, but there's something that prevented that profile from installing this software. When I changed the account type to a pure local user account (essentially downgrading, in Microsoft's eyes), all of my problems were resolved.

You are 'highly' encouraged (some might even say tricked) into using or creating or authenticating with an email address tied to a Microsoft online account.

The normal login process (local machine) that we were all used to is now referred to as 'Hello Windows'. This is 'downgrade option' of the typical local user account.

Hope this helps someone else.