and has no notation that it is American usage, or that there is a BE alternate.insofar as
to the degree that
(from Cambridge Advanced Learner's Dictionary)
Checking far, I find the three word version listed as an idiom:insofar as /= in so far as at far
in so / as far as to the degree that: That’s the truth, in so far as I know it.
In so far as = to the extent or degree that
Insofar is formal, and insofar as is formal, and in so far as is more colloquial. I will hope to be debunked or supported by a BE speaker.
If it meant because, and only meant because, I would agree with you.j0ckser said:I would offer that if insofar as/in so far as can be replaced by because, then don't use the others.