The phonetics of the word consultant is /kənˈsʌltənt/. My ears heard the part /ʌl/ is exactly the same as the word so /soʊ/. So the question is that both /ʌl/ and /oʊ/ are the same pronunciation, isn't it?
In general, /ʌl/ and /oʊ/ are not pronounced the same.
Vowels before the /l/ sound are prone to merging with other vowel sounds. Most of these vowel mergers occur in some accents, but not in others.
Related to this, in some accents, the /l/ sound itself may be "vocalized", turning into a semivowel or glide like [w] or [ʊ].
So it's not too strange that the ul of consultant and the o of so sound the same to you. But this is not considered to be the "standard" pronunciation of words like consultant, because many speakers still use different pronunciations for ul and o.