> an "unauthorized" modification of your own computer and void the warranty to install it
Citation needed. This modification doesn't look to me at all like it'd void the warranty unless you damage the machine while you do the installation.
If you need to make a warranty claim, you should of course reinstall the factory one before you do so, since the vendor doesn't expect users to replace that and won't have any practices of looking/removing so they can return it to you if you take your machine in for service with a non-Apple card there.
But voiding your warranty for this has been roundly rejected, in the US at least, as long as you don't damage your equipment by doing it.