They're charging extra for something that would cost them nothing, deny them the use of nothing, require none of their resources, if you could use it without paying them. I can see an angle for calling that rent-seeking.
The feature has already been developed, I have already downloaded the software to my device. It would cost the developer nothing, deny them the use of nothing, require none of their resources for me to use the feature and yet they charge for it.
How is that different?
I think the "it's rent-seeking" position would be weaker for toggling entire features on and off—the specific example of unlocking better acceleration was them adding a worse mode just so they could charge a subscription for the better one.