Last I checked, you’re TALL based on measurements from your toes to your head; standing on a bar stool doesn’t make you TALLER, only HIGHER.
The main island of Hawaii, last I checked, is – and by a wide margin – the tallest mountain on this comfortable little planet. No? The “base camp” there is thousands of feet (rods, cubits, centimeters) below sea-level. By comparison, Everest is one pimple among hundreds on an already-high plateau.
The peak on Hawaii may not be as HIGH as K2, of course, but the mountain is certainly TALLER.
After all, words to have exact meanings. (They change over time, but at any moment they mean what they mean.)