Suppose A and B are connected, but the connection breaks. When A realizes this immediately and sends a new (heavyweight) connection request to B, then it /might/ happen that B has not yet realized that the current connection has broken and will therefore reject the incoming request from A as invalid.
This is low priority because
the window of opportunity for the problem to occur is small, especially because in the case of a true network failure it will take some time before a new connection can be established
even if the problem does arise, A can simply try to connect again (A might have to that anyway, to find out if the network problem has been resolved).