Doesn't make any sense - there's no benefit to Intel (why would anyone order more CPUs?) and there's much more downside from all other customers.
It gives certain customers time to mitigate - and certain others time to exploit - the issue before the embargo is lifted. It maintains the customer/vendor relationship. It also allows Intel, even if current products are still impacted, a head start on R&D for future products before disclosure. Remember Intel also has their own Linux, has their own compiler suite, and directly supports development of Linux and Windows (and probably macOS for Apple) for their industry partners. So they could have been working on figuring out software mitigations during that time which they can now share.
It was not for them but for their 3 letter customers. 0 day unpatched for 1 year, what can be better than that ?