There's so much information in this post it's difficult where to begin. If the engineer is good, then promote them. Time in post is not a reason not to promote

There's so much information in this post it's difficult where to begin. If the engineer is good, then promote them. Time in post is not a reason not to promote someone, and it sounds like this manager is just crap. Often the "Time in post" requirements are just metrics that develop over time- you 'expect' engineers to develop at a certain pace, and if you're promoting them too quickly that's probably a sign that you aren't making the right decision. It's not proof that you're not making the right decision, it's just an indicator. When I managed a team I often had to manage expectations from employees that want to be promoted. Partly that was about "Look, you haven't demonstrated X,Y,Z skills" but it's also "You haven't built up the connections across the company - no one comes to you when they need an expert". Very often those requirements come with time more than anything else. The fact that the manager is having monthly meetings with the employee to check in on promotion is a big red flag. If you're not planning on promoting him mid-cycle then you've not been clear with your communication by repeatedly having meetings at which you're going to disappoint him and re-iterate the same points. The underlying fact though is this: Large companies stay efficient by under-promoting employees and only paying market rate when hiring since that's the only time there's real competition. As an employee you need to know this, and behave appropriately.