I am renovating my house and will change all plumbing system and pipings. Initially the contractor told me the pipes will run from the main pipes to the 1st floor then to the water tank and to the kitchen . However, when he saw there are plaster ceilings on my 1st floor, he changed and said to run from ground floor all the way back to the kitchen and then only go up to the water tank. I suspected he didn't want to hack my plaster ceilings and told me the pressure will be better for me. Ground floor has no plaster ceiling at the moment but will put plaster ceiling later.

Is this the right way to do the plumbing for old houses without hacking on the floor?

Thanks for all your kind advice!