Yes, you are correct. Hummingbirds have adapted to sip nectar from longer, tubular flowers. You'll notice this when you look at their bill, which is elongated, and often curved to better match the shape of the flowers. Their vision is also adapted to their food source, and they only see black, white, and red. So flowers that are in the orange-pink-purple range will stand out, with red the brightest. So the best hummingbird flowers are red, tubular, and have plenty of nectar (so the birds don't expend as much energy moving from flower to flower).
Butterflies are a little different. They have a proboscis that helps, but they just can't reach that deep into flowers. The flowers butterflies are most comfortable with are shallower than the flowers hummingbirds like. If the flowers are strong enough to support the weight, that's a plus for butterflies, as they don't hover. The most efficient flowers for butterflies will come in groups, like heads or spikes, so that the butterflies don't have to travel so far to get each sip.
And there is some overlap. For instance, out back, we have a large trumpet vine, which attracts many hummingbirds, some butterfly bushes, which the monarchs and swallowtails cover, and some agastache, which attracts the majority of the smaller skippers and cabbage butterflies. What was interesting is that the hummingbirds would often come down and visit a few purple butterfly bush flowers, but not the lavender agastache. The small butterflies/skippers will visit the butterfly bushes when the agastache was getting crowded. The bigger butterflies would sometimes attempt the agastache, but not often, and no butterflies actually landed on the trumpet vine flowers.
