I wonder how it copes with congestion outside of the home. I'd assume it can't, as it can't possibly know that the link upstream of the house is congested! All it can do is detect that packets are needing to be retransmitted or are arriving out of order, and adjust the QoS on the fly.
I cap my ds/us at 95% link speed which keeps latency down even when the link is "full" in either direction, but it goes out the window if there is ever congestion at the cab or further upstream, which fortunately is rare
Zen > AAISP Home::1 1TB > BT Infinity 2 > Sky Fibre Max