As Kot said it's stress from a sudden change in osmotic pressure and not very beneficial for the plant...
Products for leaching are usually just some sugars to get an equivalent osmotic pressure so you can leach your substrate with a nutrient free solution. Plants don't take up substantial amounts of carbohydrates, it's really just for the osmotic balance.
If you search for it you should be able to find what sugars to use and how you can approximate your nutrient solutions osmotic value. Shouldn't be that hard to figure out I guess.
But I'd recommend what Kot said, just lower your EC and/or increase runoff.
With drain to waste systems leaching shouldn't be necessary and if you do it right leaching/"flushing" is just plain detrimental.
As an anecdote:
I had cacti in extremely hot, salty substrate without knowing.
The runoff, mixed 1:2 with ro, was still above EC 3, so they were in a substrate with an EC well over 10!
But they did just fine, growing slowly and looking good. That is until I leached the substrate with tap water at EC 0.6.
A week later most got weird swelling and then startet roting!
No chance to save them.
It was the osmotic stress forcing them to take in extreme amounts of water I guess.
The point is, even extreme EC values don't have to be problematic, but sudden and rather big changes will be!