Making the company jump from sketch to figma is bit of a mission (source - I've done it before). The way figma handles frames, is much different to the way sketch handles artboards, auto-import doesn't work as well as you'd hope.
They would have massive numbers of designers, all needing visual assets. If you've got a library to provide consistency to them, moving that library over to another tool is a big mission, no matter how good it is.
I think you'd find figma gets healthy use at apple, like most of the work of UI design is trying a bunch of different solutions, collaboration and feedback, prototyping - I think figma would crop up commonly for that type of work - the 'shaping' phase.
The final step of 'ok make everything look apple' isn't that big compared to everything you've done before that point, jumping tools then isn't the end of the earth.
Believe it or not, most graphic designers are still using Adobe tools. Already hard to get them to move over to Sketch, but it's becoming the norm for digital design. Figma is popular in UI circles, but an exception outside of them.
Graphic design yes - that covers print design, print, digitla and television advertising and many other mediums - but among those designing software applications Figma seems to be kicking ass: https://uxtools.co/survey-2020/