OK, so now we're going to play a definitions game. Fine.
The full "traspaso de mando" as defined by the CN was always going to be done before Congress.
At no point did anyone indicate otherwise.
The argument was about passing the symbols of power. Baston, banda, marcha de Ituzaingo. Everybody understands this.
So quoting the Constitution in this respect is a lie. The Constitution regulates where to conduct the
ceremonial handover - banda and baston - exactly as much as it does the color of Macri's underwear at the event. (So that there's no mistake, that means: not at all).
To cover the lie of the Constitution being relevant, we come to the further lie that Macri wanted to take the oath of office at the Casa Rosada. A lie created to cover for a prior lie.
The ceremony is of symbolic value - to see the literal handover of power. Normal countries respect their traditions. Normal countries you have Carter and Reagan being as gracious as possible to each other during the transition and at Reagan's inaugural, as acrimonious as the prior campaign had been. Same for Bush/Obama.
[EDIT: You edited your prior post to add: "Also, the President decides it, not the prospect". Why? Who said that? Where and when, in the world ever, did it work that way? Does the word asuncion - inaugural in English - make it about the outgoing president (or other office-holder, for that matter) or the new one? Bias is warping your thought process.
And if the incoming president wants to depart from traditions, that's also OK if it doesn't offend anyone. CFK had her daughter hand her the atributos FFS. And here Macri is the one reverting to the tradition. Why exactly was she shutting him down over this? Because she doesn't care for the traditions, she cares for herself. She wants to turn his inaugural into her farewell, rather than do the farewell, you know,
the day before. But no. She has to make a grab for his inaugural, same as the official Twitter account.
END EDIT].
And since you bring up common law again, I'll refer you - again - to
my original rejoinder, which is as relevant here as there.
Does the CN mention the outgoing President gets to keep and rename the official Twitter account? Or can we apply common sense regarding that?