No. PROGRAM_FILES only specifies %SystemDrive%\Program Files specifically. It's a holdover from 32-bit systems, but on 64-bit systems it does not include the 32-bit installation folder tree.
There is a PROGRAM_FILESX86 value defined in the documentation, but it is not implemented for use by the Windows Update Agent.
As such it is necessary to backpath the PROGRAM_FILES common path in order to get into the ~\Program Files (x86) folder tree.