Stanley,
As NO3 and PO4 are one of the two nutrients that we can measure so we use that as a guage for nutrients level in our tank.
It is true that increasing feedings will eventually cause the PO4 level in your tank to rise but to what extend? How much feedings? Some reefers feed too much till the extend that their nutrients export could not handle and hence caused nutrients (PO4) to rise.
I feed 4-5x/day yet my PO4 still remains at 0.00 (undetectable with hanna), I can get by without cleaning the tank glass for more than 2 weeks and it still looks like it just got clean.
You probably already know that even at PO4 reading of 0.04 (with hanna) you still feel that your SPS can be better. I went thru this before and the color of the SPS is directly related to the PO4 levels, the lower the lighter/brighter the color.
To answer your "question" directly, we feed heavily and at the same time our nutrient export allows us to keep the PO4 at undetectable levels. You must remember hanna low end sensitivity is much better than your salifert PO4 test kit. Making the PO4 rise is easier (just more feedings and fatter fish, less powerful skimmer, saves electricity, lower amount of zeolites, lower flow thru zeo reactor etc) than trying to fight to lower the PO4 levels so we do have more control in this sense