AC86U got stronger 5G Wi-Fi

I used to have an AC86U a year or two before, and noticed it performed better in high channels (149~161) than low channels (36~48) in US region, the FCC report almost pointed this out as low channels has 600mw+ and high channels has 900mw+. I’d sold it after months after using it.

Recently I bought another unit of it as it seems much stable than before, flashed it to the latest Merlin firmware and found the low channels performed much better than before.

Does anyone know if they changed...

AC86U got stronger 5G Wi-Fi