Calcium is definitely needed for plant cellular structural growth and will absolutely need more during the flower cycle because of more plant mass. However, when I spray my plants, I use 350ppm of nutrients as soon as they have 5th node and I top them. Of that, in one gallon of water with a base of 7.2pH and 120ppm dissolved solids, only 10ml of that is CalMag. While I do spray in flower, I only do so up until the trichomes appear profusely to avoid any altered taste. (I dont like to taste BioWeed for instance.)
When you NEED to fertilize Ca it will be when your plants start showing an almost reverse burn. In this case, the Calcium is immobile and unable to move to the end of the leaf tip resulting in marginal burns. In my example, my water really provides enough Ca simply from hard water.
Also as a side note, I have a lot of views that differ from other growers. However, I have produced more than $175m as a Commercial Farm Foreman/Grower and my views come from my own experiences at this point. While I do confer with other growers, This season alone I produced more than 110,000 individual plants in a 61 acre facility. Therefore I don't really discuss much with others, heh. Standing on the shoulders of Giants, though. Thank you Mr. Rosenthal et al.