the 45/55 used the “Hawkeye V1” chip from Qualcomm, also known as IPQ8078/8074.
These were followed by the second version of these chips, which were rebranded as Qualcomm Networking Pro. The official advertised difference is mainly that the second version does UL-OFDMA and UL-MU-MIMO.
With that said, other vendors have struggled with enabling many WiFi 5 features: 160MHz, DL-MU-MIMO, AP to client transmit beamforming (the receive direction works), and more. That leads me to suspect there might be more that is immature or problematic about these chips and it’s not just a matter of only supporting DL-OFDMA.