We put in a ticket with SAP on this issue, they replicated the problem and said that it is "working as intended" and the official word is that you are supposed to completely delete the affected bindings & rules (after removing them from the scorecard) prior to importing, so it actually creates a new instance of the rule (new object ID).
I can't 100% say, but I feel like this wasn't previously an issue, and if you imported a large enough export (something that had bindings & rules, not just the rule) it did completely copy over the rule, but I don't have evidence.
I agree, it is a serious concern that "promotion" does not promote all changes. I submitted an ideaplace request to fix this issue and another promotion-related issue, please vote for it:
Promotion Enhancement--Deleted Rules, Rules w/Parameter Changes : View Idea