What is the difference between

Why?

It's just a way of speaking. It's like - definitely.

As, of course absent you know very well.

Exactly.

Or perhaps I should have said 'I agree with jingl', to avoid any confusion...

I think sometimes people use adverbs (if that is the correct part of speech) to increase the strength of a statement.

It's a fair question and it sounds like politician speak to me. Why can't they just say it's untrue. They just like using three words where two will do.

...........and if I hear that phrase 'hard working families' from one more politician I'll scream.....

Yes but categorically seems to be used only with untrue. I can't think of another adjective where it is used in this way.

Then it's just a manner of speaking, surely? I don't know why people can't just say "It is untrue". I have also heard "I categorically deny that".

You can categorically deny something. (have googled this categorically fascinating subject)

Oh! You've googled too Grannyknot. 'Fess up!

Okay but a) to deny is a verb, and b) categorically denied and categorically untrue are pretty much the same thing. Nobody says it's categorically hot today even when the temperature is in the 30s or 40s. In fact, nobody says that something is categorically true.

You would say "that is categorically correct".

It just adds emphasis. Makes it undeniable in any way.

Why, actually?

Did it "just enter into your mind"?

I have never heard anyone say that or read it anywhere – except in your post jingl. I'm just puzzled.

You could literally be puzzled about this, as they say

Well, someone might say it. One day. No reason not to.

I'm going to watch 'enders now. x

jingle that is categorically untrue.

Well she probably is going to watch 'enders. (What is 'enders – it sounds rude?)

It's just a bit of unnecessary tautology, surely.

Isn't all tautology unnecessary?

It is better than "it is to all intents and purposes untrue"

That was my little bit of irony absent