The AS maths course does cover some statistics and introductory calculus. It will also be beneficial for the physics course as well as it will aid you with the maths-related content.
To make sure AS maths would be enough, I would look at different universities requirements for a bioengineering course and see if this would be sufficient.
After having a quick look myself, from the few I looked at, it seemed that A-level maths and another science is required. This would mean you would need to do the full 2-year A-level maths course but it might not be the same for all universities.
There is also the options of foundation years where you complete an extra year to ensure you have the required knowledge before starting the degree properly.
But do the a-levels you have the most interest and skill in, if you’re not set on a specific career. There will be plenty of things you can do with the science a-levels.