This is what the Holy See had been teaching about the Mandatum Rite of Holy Thursday
51. The washing of the feet of chosen men which, according to tradition, is performed on this day, represents the service and charity of Christ, who came "not to be served, but to serve. This tradition should be maintained, and its proper significance explained.
The Preparation And Celebration Of The Easter Feasts
Congregation for Divine Worship
Let us read what Fr. Z had to say about this:
We can flout the rubrics anytime we want for the sake of a sentimental motive … MY FOOT.
Just because the Pope did something in some ceremony which, apparently because it was small and in a jail, mattered a lot to the inmates but I guess didn’t really change anything for the rest us – except for the fact that the Pope did it and it was ballyhooed by the powers that be all over the world, that doesn’t mean that any bishop or priest can take upon himself to change the clear and important rubrics of Mass…. any rubrics.
Take the example of Abraham and St. Joseph. They were silent, they didn't ask questions. They just followed.
This matter all boils down to OBEDIENCE. You may keep on invoking the Spirit to whatever excuse you can think of for not following what is written in the Law. It just makes one wonder if a priest like you can have utter disrespect for Church liturgical law, what other laws of the Church are you willing to disrespect and disobey?
It doesn't mean that the Pope did it, it is legal and it is the norm!
John Paul II's masses were riddled with liturgical abuses.
I am not more pope than the pope.
Just calling a spade a spade.
The pope's infallibility does not mean he is impeccable.
UPDATE: Fr. Z has another update regarding this!