Windows 10 v1709 AMA - Why has Creators Update Fall treated creators so badly?

I have the following code in our WindowProc routine that is supposed to detect if an event is a touch event and whether or not the event originated from a pen input device:

       #define TOUCH_MASK         0x00000080

       #define SOURCE_MASK        0x000000FF

       #define SIGNATURE_MASK     0xFFFFFF00

       #define MI_WP_SIGNATURE    0xFF515700

       #define IsPenDevice(dw)    (((dw) & TOUCH_MASK) == 0)

       #define IsTouchDevice(dw)  (((dw) & TOUCH_MASK) == TOUCH_MASK)

       #define IsTouchEvent(dw)   (((dw) & SIGNATURE_MASK) == MI_WP_SIGNATURE)

       // Is this a pen or touch input message

       LPARAM lMessageExtraInfo = GetMessageExtraInfo();

       BOOL bPenInput = (IsTouchEvent(lMessageExtraInfo) && IsPenDevice(lMessageExtraInfo)) ? TRUE : FALSE;

       BOOL bTouchInput = (IsTouchEvent(lMessageExtraInfo) && IsTouchDevice(lMessageExtraInfo)) ? TRUE : FALSE;

This has worked perfectly on all supported currently Microsoft operating systems (e.g., Windows 7, Windows 8[.1], and Windows 10) since it was implemented in March of 2014. Since the Windows 10 Fall Creator’s Update we have received numerous customer complaints (and confirmed them to be accurate) that the pen input reacts and behaves like a single finger touch event. This would indicate that IsPenDevice(…) macro is returning FALSE. That would imply that your pen device handler (not the driver, but your handling of driver I/O) is not propagating the 0x80 bit to the message queue.

Our user base is composed of roughly 500,000 users with a wide range of system configurations – many of which have selected the Microsoft Surface [Pro/Book/etc.] as their primary device. Since Microsoft updates tend to occur silently, many of those users are suddenly finding their pens as useless finger proxies. Your changes are affecting customers that are running older version of our product that are no longer under active support. This issue is more than just an inconvenience, it is a breaking change to existing functionality and behavior.

Having worked with Microsoft support (in various forms) since 1992, I am keenly aware of the glacial speed of getting fixes into the pipeline and out to the masses. Hotfixes are generally the quickest solution but have their own baggage. I know your cutoff for the next major rollout is probably already past. The FCU edition is one of the worst release I have seen (even surpassing Windows 8/8.1 and Vista).

Please provide me with C++ code snippets that will return the pen/touch functionality to its previous behavior.

P.S.

FWIW, this is just one of the MANY regressions in legacy Windows applications introduced in FCU.