The argument to chop later rather than early is imo an invalid one.
The amount of production gained may go up with time, but the value of production (or food) goes down much, much faster.
Its similar to real life. If i offer you 1000$ right now or 2000$ 30 years from now, you'd be daft not to take the 1000$ now.
Inflation is a bigger factor than the difference. / If you invest the 1000$ now, you'll have much more than 2000 in 30 years.
So i claim the opposite. As soon as you have improved workers (5 action or even 6), choose what you want to chop, chop those tiles as soon as you can put the production to good use. (which usually means asap, though sometimes you may want to wait for a tech, or you have an even better use like a wonder to build later)