That's not really relevant to this thread since the OP is talking about hills, where you're talking about mountains. On a long climb, I'm more inclined to stay seated and stand only for a stretch. On hills during a workout ride, I'm inclined to do some of each to get up it more quickly.

IMO, arguing against learning to pedal effectively while standing is like arguing against learning to spin instead of mash, or sprinting or any of the techniques cyclists might want to learn to make them better cyclists.

OTOH, there is nothing wrong for striving for just mediocre for some people - it's just not for me.