Actually, I have always wanted my children to play with Tinkertoys and marble tracks because you actually have to think of where things go in order to build something that works. You can just keep piling LEGOs up to get where you want.
SO if she wants to dumb down the girls, more power to her.
Of the three I would say that tinkertoys are the most open ended and allow the most inventive designs. They are much more efficient than legos since you’re basically building a framework rather than filling in a bulk area. I remember as a kid not being a big fan of legos because they were so dang tedious.