80 / 80 is sure close to reality.

As alternative explanation, even if there's no pressure to do so, the thing is these people came to do dev, and probably enjoyed their job enough to get recognized for their work.

So when asked to split between dev and management, outside of a few exceptions they'll want to do 80% of tech by choice. But the management part doesn't go away of course, so it will still be at least 50% (and 80% if they want money, because that's the part they're actually evaluated on)