Per API documentation, the Decimals property defaults to what is set in the user's region (culture). This is a flawed design.

Why would one think that ALL properties of type double or float in grid models should be truncated to 2 decimal places (when my region is set to US and that is the default)?

This seriously limits property values. Not everything is a dollar and cent value! The region setting I believe is for how to format general currency values perhaps (I am not exactly sure what it is for, because there is a different tab for 'Currency' with a 'No. of digits after decimal' setting as well as the tab for 'Numbers' having the same thing. But this does not mean that Windows always formats numbers that way.

Suppose for example I have a property in my model named "Weight" (expressed in terms of pounds). The value 150.12345 (pounds) is perfectly valid. It should not be truncated to 150.12. Or another, "Length" (expressed in terms of Feet): 17.0625 (that's 17 feet, 1 inch) - should not be morphed into 17.06.

To work around this, developers currently either have to override a <GridColumn>'s <EditorTemplate> and place a <TelerikNumericTextBox> element bound to the same property that the <GridColumn> is, and explictly set the Decimals property themselves.

Or what I have found is a better workaround, although not desirable to have to do this at all, is to put this kind of code snippet in the Program.cs file, right after the line var app = builder.Build();

app.UseRequestLocalization(action =>
{
   var currentCulture = CultureInfo.CurrentCulture.Clone() as CultureInfo;
   currentCulture!.NumberFormat.NumberDecimalDigits = 10; // for example, to allow this many decimal places in everything numeric
   var cultures = new List<CultureInfo>() { currentCulture };
   action.SupportedCultures = cultures;
});

Please remove the default value for the Decimals property being tied to the culture. It should just allow as many decimal places as a normal float or double would allow for its precision. Perhaps just allow a developer to set it and honor that, but if not set, basically let it be unlimited, just like the number of digits to the left of the decimal point.