Maya anim curve issue

Hi all, we’re doing more dev work on our Red9 anim format and have a test file that fails our unitTests BUT as far as I can tell the anim curves in it are actually illegal?

Basically we have curves on one attr who’s keys look to be linear, but actually have key tangnts that have zero weight, yet the curve isn’t even set to be weighted. In the API I’m not even sure how you’d do that, and in the UI I definalety don’t think it’s right, yet the file loads in Maya quite happily and I must have generated it at some point. Any idea?