Accuracy of LAI Computation in SNAP

I would like to know how accurate is the LAI module in SNAP.
How does the accuracy of the product vary from deciduous to coniferous forest type?

I think this is hard to answer.
At first, it is not only the mathematical derivation but also the quality of the data and its radiometric calibration, but also the type of vegetation (a coniferous forest in Canada differs from coniferous forests in Portugal). So I would be very careful to draw fast conclusions on the quality.

I see this module similar to a supervised classification, for example. Technically, you can apply it to any data and class typology but in the end you are the only one who can tell if it makes sense because you know your study area best. And as for each accuracy assessment, you need field measurements for comparison.

But you are right, the SNAP help does not tell much about the actual methods and their calibration. Maybe there is a document with a quality test around.

I could find these publications which tested the quality of the SNAP processor: