Yes, we use Mehlich 3 here, so I am very much aware that Mehlich 3 does not have P1 and P2.
However, the OP did post this:
"Albrecht is quoting the Mehlich 3 above."
And later on he is talking P1 and P2.
And so, I am questioning..... and my post was really directed to the OP.
I was looking for him to respond.