Perhaps it turns out that a luminance value that can be defined as the total light flux divided by the light emitting surface area does not 1 to 1 predict the throw because it does not take the spatial distribution into account, and even then spectral shifts with changing angle can have an influence. In theory, an ideal spatial distribution for throw may be different for reflector lights and for lights with aspheric lenses.
If the aim is getting a value for any particular led that directly gives potential throw, maybe an empirical approach for measuring it must be devised. I have an abandoned project for testing reflectors (as always I found designing the method way more fun than doing series of measurements using the method) that when used the other way around, with a fixed reflector and a fixed aspheric lens (say, a C8 reflector and Brinyte B158 lens) and varying led, can be made into a standard method for measuring throw. Spot intensities can be measured with all leds at a standard current, and the current/output graph from the output test can then be used to calculate the maximum throw.