That's good advice.
The main concern about chicken manure is the risk of a contact burn - that shouldn't apply to your composted manure, but it's another reason to scratch it into the soil.
Either way, chicken manure will tend to have lots of free N, and that is soluble. So if it's worked into the upper soil, it won't be washed out as easily before the plants can get it. If it was in the bottom of a hole, any rain or watering would tend to wash the N down further below the root zone, I reckon.