We know this not to be the case, both from our previous experience with our other kids but also because, anticipating their argument, we have had DS working out of the 5th grade Saxon math book in his free time and we are finding the content to be virtually identical.
If you are confident of this, and if you think they are reasonable people who would accept a fact-based, sensible argument, I would consider pointing it out and asking them where they think the two programs differ. At least you can mention it in passing and if there's anyone there who cares about whether what they're saying is true, they will at least take a look. If not, you know there may be other things going on (for them to ignore what they've said) but at least you've brought it to their attention so if they really care they will act on it. Perhaps what they looked at is not what you're looking at, and maybe there is some kind of difference in the order that subjects are presented in the two programs that would lead to the conclusion they've drawn. Good luck!
