Logical wal receiver (background worker) not detecting when publishernode has died

Dear List,
Coming back from : 
https://www.postgresql.org/message-id/ae8812c3-d138-73b7-537a-a273e15ef6e1%40matrix.gatewaynet.com 


and having got absolutely no helpful answer from our infrastructure 
people, I would like to ask :

Is it on earth possible that the primary (publisher node) has crushed 
while on the subscriber node the logical wal receiver goes on happily 
like there is no problem at all, no messages in log, no timeouts, acts 
if nothing happen ?

(in the meantime the second standby instantly detected the crush of the 
primary and immediately restarted re-connection attempts)