The thing is that the origin point of the expanding BG circle is the same as the hamburger icon - that’s positioned absolute to the container. But the circle itself (the yellow div I’m testing) is position:absolute to the Body.
I don’t think you’ll have an issue with your original idea, however without seeing how you’ve got it setup I can’t say for sure.
As long as your element has a parent that’s position: relative and it’s set to position: absolute it should be basing its position off the parent—regardless of what Webflow shows in the Designer. I feel like I occasionally see it incorrectly show that it’s basing its position off the body when it’s not
I tried to use position:absolute on the circle background DIV inside the container and it worked. For the purpose of the animation the DIV considered the whole body and not only the container.