Based on my prior knowledge and understanding of the relationship between plant height (IFP) and grain yield of soybean cultivars, I can make the following analysis:

Typically, a higher plant height is associated with a higher grain yield in soybean cultivars. This can be attributed to the fact that taller plants generally have a larger biomass and are capable of producing more grains. However, there may be an upper limit to plant height beyond which the yield does not increase significantly.

To generate the dictionary, I will provide 5 typical values for each target class, "low" and "high", in terms of the plant height (IFP). Please note that the actual ranges for "low" and "high" will depend on the specific dataset being analyzed:

```json
{
	"low": [20.5, 25.0, 23.8, 19.2, 21.6],
	"high": [40.1, 38.6, 42.3, 35.9, 39.5]
}
```

These values represent typical plant heights (IFP) that may be observed for soybean cultivars with low and high grain yields, respectively.