Thanks for the info.
For the sake of others who might look at this post later — The REG key isn’t quite the same as the previous OSVERSION, as it omits the OS architecture. But I was able to create an exact match by combining two items with a user variable. Here’s the code for anyone that needs it:
REG=active:2,interval:0,value:HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\ProductName,wow:64,set:ProductName
WMI=active:2,interval:0,namespace:root\cimv2,query:Win32_OperatingSystem,display:%OSArchitecture%,set:OSArchitecture
TEXT=active:1,interval:0,style:b,text:OS Version,display:%ProductName% (%OSArchitecture%)