> Tying (informally, product tying) is the practice of selling one product or service as a mandatory addition to the purchase of a different product or service

MacOS isn't sold anymore, it's a free download for all supported Macs - meaning Apple is not "selling one product or service as a mandatory addition to the purchase of a different product", regardless of which product you think is being tied to the other (hardware or software).

I can see where you're coming from, but Apple wouldn't necessarily be in trouble due to the wording of the law. Maybe in some countries where the spirit of a law matters more than the specific wording, but we're quoting US legal definitions here, and my mental model of the US legal system has the phrasing mattering more than the intention