I made another inquiry with AudioPro and got some additional information:
The WiiM Edition "got a completely updated system root. So it will have full functions with other Wiim devices.
It supports more streaming services etc."
They also assured me that LinkPlay support will be maintained for the vanilla AudioPro devices, so there should be no concern about the devices eventually failing to function as netorked LinkPlay devices.
Even if the difference is only firmware, I recognize that WiiM is under no obligation to facilitate a firmware upgrade to the products I purchased from AudioPro. However, it would be a nice gesture (if it is even possible), given that rapid pace of evolution in the WiiM/Linkplay landscape, and my investment no fewer than 4 WiiM Pro+ streamers. If I had known that WiiM would be formally adopting the pre-existing LinkPlay-compliant AudioPro hardware a mere month from my purchase date, I probably would have held off the purchase...