It is not a question of how far they reached. It is a question of what DJI spec say - and for EU/CE that is max 5 km.
But lots of things can change wireless conditions.
But in any case you should not be so far away from your drone unless you have a spotter. You can't see if a small private plane or heli is coming towards your drone at that distance.
So from my perspective you are trying to ruin drone flying for the rest of us.
Italian rules; " Your drone must remain closer than 200 meters (650 feet) away from you, and max 70 meters (230 feet) high. " - I will agree the Italian rules are a quite on the strict side but....