On the face of it that sounds like a burn on Microsoft, wisely found by studying the finances, but... by the nature of Apple being the best performing stock in the world for multiple years isn't the same true for most companies, that they could've made more money investing in Apple than in themselves?
Heck, maybe investing hundreds of millions in Apple today would, in X years, be worth more money than spending marketing money / development budgets for new features for their own products; or worth more than investing in OpenAI and related products - but it's not exactly something anyone would suggest Microsoft should do (in terms of just becoming a shareholder, of course there could be collaborations without changing this point).