That will flower plants just fine. I used that very brand and strength in powder form for a year when I started growing.
Beware of the growing elites. They'll have you spending 20 times as much money as necessary because they heard something was bad or good on the internet. Then there are those of us who grow or have grown with the basic ferts like Miracle Grow, Schultz, Peters, et.al. and can tell you they grow great tasting and healthy plants, all the way to harvest. Anyone who says otherwise is talking bullshit.