My point in the example was that, if you don't say "joined-up" in relation to writing, they won't be likely to be sure what "joined-up" means when it comes to thinking.

Another example might be, in a place where all the cars are automatic, imagery about "getting stuck in first gear" and so forth can't convey too much.

And the same kind of thing is liable to happen over time - if we all end up wearing foot gear with velcro fastening, phrases involving bootlaces would be marooned.

I'm sure there are lots of examples of that having happened, where we still use the terms,but with no idea of what they actually refer to.