Qualcomm's Thread implementation sends a short address in the beacon instead of the extended address. Section "3.2 MAC Layer" of the Thread 1.1.0 Specification modifies section "184.108.40.206 Beacon generation" of the 802.15.4-2006 Specification to ALWAYS send an extended address. See Table 3-2. Modifications and Statements to Chapter 7 and Annexes of IEEE802.154 ( https://standards.ieee.org/findstds/standard/802.15.4-2006.html )
From the Thread 1.1.0 Specification:
"The address used in the Source Address field of the beacon frame generated by a Thread device SHALL contain the value of aExtendedAddress for all values of macShortAddress."
The ramifications are devices that conform to the Thread Specification reject the non-conforming beacon and are unable to join networks where a QCA4020 is acting as commissioner.
FYI, I first notified Qualcomm of problems with the beacon back on June 3, 1019.