The profile in the bottom screenshot show the total overall profile- in the total of the water. That’s why the amount in the profile doesn’t double- that’s not the profile of the mash water, it’s the total profile.
If you add your salts to the mash only, or split it among the mash and sparge, it’s the same amount of salts being added to the same volume of water.
To put it a different way, say you are making iced tea and I am making iced tea. We are both making one gallon.
You put 8 teabags in a 1/2 gallon and then add 1/2 gallon of water. I put 8 teabags in the full gallon, and don’t add any water.
We both put 8 teabags in a 1 gallon volume total. So the make up doesn’t change at all.
In the case of mash/sparge water, the mash pH may change because some of the salts drive down pH slightly (or up in the case of alkali). But using 6 grams of gypsum in 10 gallons of water gives you, say, 108 ppm, whether you add it to 5 gallons and top up with 5 gallons or adding it to the total of 10 gallons.