because bard's E would also allow his entire team through, literally being a counter to any and every terrain forming ability. Also it would have to take into account the fact that the terrain can disappear by itself, so what would happen to his E if the champ-made terrain would disappear but the E duration would have out-lasted it.
Whereas talon's hop/parkour is just himself and it's fast, not an ability that remains for a period of time nor can anyone follow him unless they have an ability that lets them jump to allies (like jax's Q) or they blow their own obstacle-jumping ability to do so (flash, trist jump, etc)