The feldspar contents are quite high - 18-34% K-spar,...

The feldspar contents are quite high - 18-34% K-spar, Plagioclase and muscovite mica. That is not particularly well weathered granite. The -45um fraction is just the dust liberated from crushing the sample. If the sample did not have so much un-weathered material then yields of -45um fractions would be higher, and obviously what halloysite is in there would be greater.

THe more un-weathered minerals there are, the more tough and harder to dig and process the material will be, so having up to 60% un-weathered mineralogy (feldspars and quartz) is not looking ideal.

So.

LRS needs to go find more saprolitised granite, to improve the characterisation of the material, and find something that is softer, contains more good stuff vs gangue mineralogy etc. These are very sub-par results I would think.