I've just been helpfully shown paragraph 1.25 in the explanatory memorandum, which deals with this exact matter:

The exclusions for certain payments from the SG framework were previously set out in both the SGA Act and the regulations. No change is being made to the exclusions, but they will all be consolidated in the regulations to improve readability of the legislation. It is appropriate that the exclusions are set out in regulations as they are technical and specific exclusions to the general law.