Well, you have to remember that the concept of high and low light is really quite poorly defined. Also, some plants stall under low light, i.e. they become "low light" plants that grow at a snail's pace. If you want to sell a plant that develops quickly and satisfies the customer then of course you will suggest high light to speed the growth. Again it should be clear in our minds that high light is OK if flow and CO2 are also high, but how often is this the case? People, especially newbies and those migrating from fish only tanks just can't wait to dump a bunch of fish in the tank and that limits what they are able to accomplish because they have zero skills at CO2 implementation and the fish suffer easily when the tank is incompetently dosed with CO2. They then always draw the conclusion that if the fish are suffering hypercapnia then it must be that there is plenty of CO2, so like lemmings, they add more and more light and the tank falls off the cliff. The situation is completely out of control because everyone thinks they are running the underwater equivalent of a cannabis farm.
The fact is that each plant has a property known as Light Compensation Point (LCP). This is the minimum amount of light that a plant can use to make carbohydrates. A plant operating at LCP intensity levels is only able to make exactly the same amount of carbohydrates as it's cells burn. If the light intensity falls below LCP the plant will starve to death. If the intensity is raised above LCP then the plant can manufacture excess carbohydrates and can therefore support a higher mass, so it grows.
A so-called "high light" or "medium light" plant does in fact have a higher LCP than a "low light" plant. This is indisputable.
What is in dispute however is how much higher is the LCP of a high light plant than the LCP of a low light plant?
Ferns, mosses and anubias can grow with as little light as 10 micro-moles or lower. They can practically grow in the dark.
On the other hand plants such as Glosso, Ludwigia or Hygrophila will have a high LCP, maybe 25 micro-moles or thereabouts. This is still pretty darn dim even if the LCP value is twice as high as for moss.
If you grow a high light plant under low lighting then it will automatically behave like a moss or anubias. It will grow painfully slowly - but the probability of melting and destruction is also proportionally low. If you apply high light to a low light plant then you need massive amounts of CO2, otherwise there is a high probability that it turns to mush.
But people don't want to hear about, or even look at a 25 micro-mole tank. It's too boring, so they pummel the tank with hundreds of micro-moles. That's when the trouble starts because plants also have a property known as CO2 Compensation Point.
You can probably guess that this parameter describes the minimum amount of CO2 required to make enough food to feed all the cells.
Naturally, it turns out that the plants which have a high LCP also have a high CO2 Compensation Point.
Unfortunately, as we well know by now, it's 10,000X easier to get lots of light to the plant than to get lots of CO2 to the plant.
Light has no trouble traveling through clear water. CO2 and ALL gasses have major difficulty moving through water.
So while the nurseries are correct in their labeling of the plants, in practice, it becomes a disaster.
Carbohydrates grows plants. Light allows the plant to make carbohydrates.
More light results in faster and more voluminous production of food.
So in a high light tank, everything happens faster, both the good things like growth rate, as well as the bad things like algae and nutrient deficiency.
Managing a planted tank and keeping it problem free requires understanding the relationship between these factors.
Cheers,