I don't know the solubility of THCA in anything but I do know that solubility and leaching of plant material is not the same thing. Maybe the nature of the secreting cells and their contents is such that there is an equilibrium between the plant material and the IPA for the THC(A). Obviously the plant material will absorb ever-increasing amounts of THC(A) with concentration.
A chemist would extract with fresh solvent, usually 3-4x if not in a continuous extraction device, or assisted by ultrasound.
A chemist would extract with fresh solvent, usually 3-4x if not in a continuous extraction device, or assisted by ultrasound.