I use a similar practice for a lot of my larger beers (1.080+); basically, I like to give the yeast a good 4-7 days to process the complex sugars extracted from the grains, and then supplement with whatever additional (simple) sugars I plan on adding afterwards. I.e., my most recent IIPA had a target OG of 1.096; I hit 1.086 after the boil, but planned to add 1lb dextrose as well. I gave the yeast 4 days to chew up the main portion of the wort, then added the dextrose (boiled in some water, of course).
As to whether it'd impact the overall taste or flavors, that would depend on the volume of sugar you're adding and the OG of the beer in question (prior to sugar additions). Larger brews such as the one I listed above can tolerate a bit of simple sugar addition due to the small percentage of fermentables represented by the sugars themselves. I wouldn't recommend the same practice in a beer with an OG of 1.040 or so, because the ratio would be significantly higher.