Packetloss is an unwanted phenomenon. When RTP is used (as in VoIP), dropped packets cause degradation of the sound quality. Another problem of packetloss is that it slows down TCP connections. TCP was designed with an assumption that all packetloss comes from congestion. When a packet is dropped because it was changed by noise, TCP thinks the link is congested and slows down. More detailed explanation why TCP slows down is on Wikipedia.
Ronja link typically runs at bit error rate (BER) better than 10^-9. That translates for frames 1500 bytes long into 0.012% packetloss. It's not uncommon for radio wireless links to run with packetloss of 1%.
When a fog is coming, Ronja has only very narrow window in which it has packetloss. The drop comes very fast. Therefore for practical application it can be assumed that Ronja link either doesn't work or has negligible packetloss.