Nailed it. I suspect the OP is a waterfall guy (despite the token references to agile). All the references to documentation is a big clue. When I see "documentation" and "development" running in parallel, as if that's an extraordinary thing, I mentally cross out "documentation" and replace it with "input from stakeholders", which, in an agile world is... YES!! Of course those run in parallel. That's the whole point of agile.

How do you translate "send an email to users" as a feature without a Document? ... also an incredibly waterfall thing. We Don't Do That Anymore. Thank goodness. Because it is incredibly inefficient (and not any less error-prone). And the chances that Some Guy who wrote the Document six months ago really understood the actual problem is...practically zero.

One of my favorite waterfall stories. A friend of mine who does contract programming for <big company>, who said that her projects were always delivered exactly on time, so you never had to apply the "double the estimates rule".

"So your projects always finish exactly on the delivery date original given?!" Incredulity!

"Oh no. They usually take twice as long, but the difference is that, first we deliver what they asked for (which arrives exactly on the original schedule date, but is completely unusable); and then we charge them 3 times as much to deliver what they actually wanted (which takes twice as long)."