My impression was that "it works", but doesn't show the correct information to the player.
After you have cast Thaumaturgy and started a conversation, when you have an Intimidation dialogue option, if you hover on [Intimidation] to see your bonuses, you don't see Advantage. Only your proficiency and Charisma bonuses.
But if you select this Intimidation dialogue option nonetheless, on the next screen, where you roll, you can hover over the roll target. There, it should show that you have Advantage.
So, at any rate, it's not working well.