Now this is just my opinion, but an opinion that has had 35 plus years of growing experience.
Mostly nursery stock, and stints of growing MJ. When a plant uptakes N,P,K it is metabolized, so I do not know what people are talking about flushing out.
You would have to flush out the cells of the plant, leaving nothing, to flush out the nutrients.
Miracle Grow is a good sterile starting medium. Me personally I use a mixture of soil, sand, and manure.
Afterwards I do use liquid MG, enhanced with some micronutrients. I will at times use 10-34 or 28-0, both are quite tricky and can burn easily.
Liquid MG is very hard to burn plants, but can be done.
Look forward to hearing more of people input.