I think you may have misread my comment. ARIN ALLOWS the issuance of /24s to multihomed enterprises. The recent policy decision was made to allow upstreams to do this sort of allocation, without having to receive any other justification, other than multihomed status. This could seem to be RIR recognition of /24 as the globally routed "common denominator" - for those who insist on basing their filter policies on ARIN guidelines. :)
ARIN also _allows_ the issuance of /32s to anyone. They, however, do not issue /32s directly, nor do they issue /24s to multihomed entities directly, without heavy justification. As such, the ARIN allocation would be the larger aggregate from which the /24 is carved. If ARIN were to (as I believe RIPE is presently doing or trialing) begin assigning controlled amounts of small multihomer space from a specific netblock, then we could filter knowing roughly what the longest prefix is which contains the largest aggregates of all assignments. However, this would be up to the RIR, and they certainly don't have to do it. The RIR published data provides just that: They say for a specific range what the longest prefix is which is expected to not be further aggregatable. As such, responsible filterers will know: 1) at what point, if they were to filter, they would be likely to filter away folks who CAN NOT further aggregate (which is bad) 2) at what point, if they were to cease filtering, they would be receiving ONLY more-specifics. The onus then moves to the assignees to announce their largest aggregates, and should they choose to deaggregate beyond that to /32, becomes a moot point (except to those who don't filter). Anyway, I'm done, if anyone wants to discuss this further with me, mail me direct.