I don't like that at all. It should be top 3 in each heat. 1500 championship races are rarely run for time. I'd much rather see the three best in each heat get in instead of six people from some lucky heat that goes fast - often heat 3.
So I'd rather see 3 and zero. I think it's much better to make sure a potential medallist (top 3) is guaranteed of advancing.
Actually, with 26 entrants, I'd personally rather just see 2 heats. Run a two turn stagger and it will separate itself out but that would be pushing it.
Speaking of heat 3, look how loaded heat 3 is - Hassan, Seyaum, Houlihan and Arafi.