That is true. But it's a long time out. 42.5 minutes and the trader still has to keep waiting for the resources for a sizable push. I get and agree the advantage keeps growing, but my gut tells me the first 40 minutes are more decisive. I run this often, and many times I'm the defender around 40 minutes, easily win, then push in. Assigning defenders advantage to the trader assumes a world where more than 1 person does what I do, and thats not the world we live in.
In a game situation he would probably not wait too long but slowly and steadily push you as he has way more gold.
If your opponent tries to push into your bigger army and loses his forces there, that's of course a huge disadvantage for him, but it's also a huge misplay by him. A player that realizes he is behind in army and needs to defend an all-in push should not attack. Then again, if he still does it's just not well played. I just don't think it works as soon as you reach a specific ELO at all. Until then you have a pretty small time window of opportunity you need to use.
I don't quite get your last sentence, but if you think the tactics just works because it is rarely done and therefore nobody expects/defends against it, should you really propose it as an better overall approach?