If the moon is still receding, then now a greater moment of inertia mr^2, and lesser angular orbital velocity. For earth, might there be a related (?) change in angular velocity (lower), and hence in angular momentum; but no momentum exchange with the moon? But still could one have both conservation of angular momentum, as well as momentum exchange, for variously considered closed systems?

For a closed system, one can have exchange of momentum. Did the solid earth core form comparatively early; 100 million years? If so, then there would be a shift (decrease) of mr^2 moment of inertia i.e. mass re-distribution to a lesser radius. Would this then account for a compensatory increase in moment of inertia (i.e. increase in orbital radius) for the moon? Might the moon`s present increase in orbital radius, in part be due to a continued radial inertia, from such long ago earth`s change in moment of inertia? Early on, did one even have some concomitant increase in angular velocity for earth, consistent with core formation and conservation of angular momentum for earth?

Rheologically, the earth seems quite quiet in regards to differential rotational motion? Such as for core – mantle interface, wherein deep plumes seem to be fixed. Also the solid core has perhaps just slight rotation. The asthenosphere (upper mantle) apparently has some flow; always in step with lithospheric plate motion? Still insufficient to contribute to angular velocity and momentum?

Are there any other possible contributions to any conservation of angular momentum, or momentum exchange, if earth is considered as essentially a solid rotating sphere?

Might there have been more than one planetesimal collisions with proto-earth? However might there not be any isotope compositional differences, since all such objects in close orbits, and hence a shared solar nebula environment?

Mercury has a strong magnetic field, and hence fluid interior. Yet Mercury has essentially no precession. Might this be consistent with no internal comtribution, nor planetesimal collision, contributing to any hypothetical precession? So any lack of precession for Mercury would seem consistent with no internal dynamic changes (such as mass re-distribution, nor significant rheological changes) contributing to a hypothetical precession.

While for earth, precession of the equinoxes, and resultant changing polar star, gives only one periodicity i.e. one frequency. This would seem consistent with only one collision, with resultant external torque changing the angular momentum vector. Whereas multiple planetesimal collisions with earth would seem to give multiple periodicities.

If earth`s rotation is slowing down currently, might this not be due to earthly influences, but rather to momentum exchange with the sun? That is, increasing angular velocity, and hence momentum of our star? Likewise momentum transfer for Mercury, which is in 3:2 resonance with the sun i.e. 2 rotations per 3 orbits?

Might such scenario of momentum exchange for a closed system be considered as an example of entanglement, wherein the system as a whole has to be considered in order to fully explain observations? So can both conservation of angular momentum and effectively exchange of angular momentum be considered in concomitant descriptions?