Yeah that's cool for sure, it's definitely a great way to do it but it's less than half a mm of both sides and I don't think the potential misalignment would throw much off. I have done it with a Dremel and with a unibit, take you time and do it well and it's fine.
The way my disc brake front is set up on my pinto with mag mk2 hydros, it doesn't drop out so it needs the axle to slide, lots of different ways to skin the cat just gotta choose what makes sense in the context of the build.