I dont think rlys action regarding links are justified/not. But when you start conversation with some LP or any other staff those who know about the link will give you an answer like, which ever loco is available we use it for xyz train(xyz can be any train and sometimes at HWH and NDLS I came to know about WAP-7's that they are specifically for the Rajdhanis and long hauler with lots of stoppages).
Coming to the voting topic, When Poorva was in ICF mode , it had 24 coaches and ICF coaches are heavier than LHB so why they didn't gave WAP-7 earlier as the way Kalka was provided.
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WAP-7 are to provide hotel load to the LHB coaches then its fine, but again we cant find any of the HOG WAP-7 working with their HOG on. So it's my opinion rly has rights to assign link as per their choice and availability.
Now soppose if WAP-7 comes to SER, to which train they will provide the WAP-7, 12839/40/41/42 -Durontos-shatabdi's or to AC SF's(plenty of high patronage trains). They will provide WAP-7 to the train which really needs it, it's that simple.
So in the regions where WAP-7's aren't available , WAP-4's are doing awesome service. Hence it depends upon the section and ultimately to the controller for the punctuality.
Lastly - for WAP-7's ,group them up.
HOG WAP-7's - only for pure LHB/Rajdhani's
WAP-7 - For Heavy hauling (Trains with 24 coaches and lots of stoppages).