Would pretty much be impossible to guarantee 20mbps upstream really wouldn't it...
In my eyes that looks like FTTC with a higher support plan so that it guaranteed to get 20mbps downstream, not much different to someone who gets BT Infinity estimated for lowest of 35mbps... BT would guarantee 35mbps or drop the connection if it wasn't possible
Minusnet 21CN 3500/800 @ 4.2Km > TP-Link TD-W8968v3
Minusnet Fibre 67000/19999 @ 450m > HG612 > Asus RT-AC87U BQM