AFAIK its not.. u r not allowed to board train if u have change boarding point, TTE may allow u bcoz of availablity of seats is different scenario or TTE was not strict but what u said that TTE also said the same is unbelievable bcoz either TTE self dont know the rule but its contradictory as SHATABDI category premium trains have Sr TTE..
However here is the rule
"In case a passenger has changed the boarding point he will lose all the rights to board the train from the original boarding...
more... point. If found travelling without any proper authority to travel, passenger will have to pay fare with penalty between original boarding point to changed boarding point."
.
click hereLink and SS both attached