The house next door...or how to NOT build a house

[Frank S]

If I had to make a guess I'd say they are going to pour a unitized floor foundation and basement walls.
I would hope they pour the floor then set the forms for the wall/ foundation wait a few days for some curing to take effect then pour the walls.
I've seen contractors try to make a pour of the walls and floor all at once but that hardly ever turns out well.