Their requirement for it applying to all people make it generally universally true. If you have a dedicated IP with reverse DNS pointing to an A record on the p

Their requirement for it applying to all people make it generally universally true. If you have a dedicated IP with reverse DNS pointing to an A record on the primary domain that server is responsible for, and you have SPF, TLS and DKIM running smoothly, it’s very unlikely any spam markers are due to the fact that you’re sending mail from <regular Ip> instead of <Microsoft 365>. This doesn’t mean you’ll never be in the spam folder, it means your spam reputation is based on the content and frequency of your emails.