This is not correct. Android has 150+ patches to Linux last I checked. It is not insignificant. There is not a good collection of patches to simply apply to a kernel of your choice either. Additionally, there are often many modifications made per-device or company (E.g. Samsung) or hardware configuration.

Finally, many of those patches are unlikely to make it upstream anytime soon, as they are usually controversial.

Please don't spread these falsehoods.