this isn’t always the case and very often incorrect. Yes higher medium ec means the plants are not eating nutrients at the same frequency and ratio as your feeding. But a spike in ec is not usually the plants doing. Ec spikes are contributed to water content going down faster than nutrient uptake is happening. Wether do to the plant sucking up water or evaporation. When feeding coco it is our job to regulate this keeping water content in check which in turn will manage your EC.
The second issue with your statement is flushing with pH balance water. In coco you never wanna do this. Because Coco has a cat-ion exchange rate higher than most medium it naturally will latch on to magnesium and potassium. This action makes it so that even when you’re feeding nutrients into your medium the plant will not have access to 100% of the magnesium and potassium you are feeding because the coco will hold onto some of it. Flushing coco with only ph balanced water will most definitely mess up the cat-ion exchange and nutrient balance in your medium causing lockout and deficiency. If you ever flush I recommend flushing with the exact ec you want your plant to be at u til input ec = output ec. That is a reset.