Keeping within 5.5-6.5 PH with the target PH for method of grow adjusted at start of feed is all you need.
Then retarget when going out of range for hydro.In soil watch out for PH altering amendments.
Are you sure you are not confusing a swing to 7 PH (in veg) than starting out at 7 PH?
Or do some growers start out with a high for plant PH for a bloom phase down swing of PH?
7 PH for veg is not good,and 7 PH for flower is experimental and strain dependant.