Following Noether's theorem conservation of momentum relies on translational symmetry of space which we assume but have no proof for (other than measurements of conservation of momentum). In so far it is theory territory.

Thermodynamics on the other hand relies only on effects of large numbers (of hard balls) with no further assumptions. In so far I can understand the GP assertion although I am reluctant. You put in the hard ball assumption (particles can exchange energy) which may put it in theory territory. As well the laws hold only for equilibrium situations which can be reached in (sufficiently dense) baryonic matter but maybe not for non-baryonic matter.