Are there fuel flow and hp numbers to go along with those bsfc numbers?

And no a/f ratio measuring during that session?

By looking at how much higher the bsfc numbers are at the end of the pull, I’d say you were probably running the motor at a high enough to see the hp curve start heading down.
Even if the a/f fuel curve is pretty flat at the top end of the pull, if you’re running the motor high enough to see the HP start falling off...... the bsfc numbers will start to go up.
The rpm is going up, and as long as the valvetrain isn’t doing anything odd, the air flow should still be increasing with rpm.
More air flow pulls more fuel in with it.
So, you have air flow and fuel flow increasing..... at the same time the HP is decreasing........ and the result is the bsfc/bsac numbers are getting worse.
You’re using more air and less fuel...... and making less power with it.
Even if the a/f ratio was perfectly flat....... the bsfc/bsac numbers would still be going up.