Both matches sir!!!
I havnt discussed about Kannur or any other specific stations!!
Simply, if ur station can permit, u can opt other routes (& it simply specifies, if it doesnt, u dont have other option left)
There too, i have discussed the same, all trains cant be diverted, on the ground of NZM-TVC/NJC etc connectivity, as intermediate public uses the train & thats...
more... why, IR transhipped via Bus, recently. But someone going to NZM-ERS, can opt Kerala over Mangala under these circumstances & thats definitely choice/availability based.
Here too, Train Diversion isnt been discussed, but people option been discussed, based on station combination, choice & risk minimising factor!!