I think you are on the right path, it also explains why Russians are so good at Math because сколько is a 2 syllable word vs. "how many" 3 syllables and two words.

To be serious, Russian morphology restrict the number of short words. A verb or a noun will have a suffix that changes by plurality, case, gender, tense etc. and often a prefix. E.g. a pretty common word such as "come" in "Come to dinner with us" will have four syllables in 'заходите' because its root has a vowel, prefix has a vowel and suffix has two.

Question words are grammatically pronouns in Russian so they have all the morphological features of nouns.