I'm following as a layperson, can you explain how to reach your takeaway from the bullets presented? It seems like #3 is almost identical to low-end normal conc

I'm following as a layperson, can you explain how to reach your takeaway from the bullets presented? It seems like #3 is almost identical to low-end normal concrete, so "good idea". Not sure what "24h" vs "2h" refers to though.