Done the way I described, probably yes, fitting with the fall shrub cuts. But if you don't do the grass turning thing and only rely on compost for the top (and you have enough compost ready), it may be instant plant, p.e. for tomatoes. Never seen it done in reality, maybe prepare for some or much caving in when all those cuts settle. You might however get an early start due to the heat generated, especially if you use grass clippings for the layer under the compost. But beware, not too much, had to put out a fire some years ago from some person who thought the more the merrier. Don't underestimate the heat generated from a big heap of grass clippings.