I think it is going to depend on the individual fish as to how they swim.
I have 5 Redtails. Out of the 5 only 1 swims at 45 degrees. All the rest swim normal. I think the only reason the 1 does is cause it's the little guy and is trying to be incognito.
I have had 3 Rhaphiodons, still have 2. None of them have swam at 45.