Question: Is Genesis 12:2-3 actually a covenant? Wouldn’t it be more accurate to simply call these verses promises?
Answer: If Genesis 12:1-3 is taken in a vacuum, then we might not consider it a covenant, simply because it is not specifically identified as a covenant in that context. However, when God reiterates and expands the promises of 12:1-3, He calls them a covenant (15-17), Later  in Acts 3:25, Peter affirms this characterization by referring to 12:3b (and 22:18) as part of the covenant. In the same way 2 Samuel 7 never refers to God’s promises to David as a covenant in that context, yet in instances afterward David and God refer to those promises as a covenant (e.g., Ps 89:3).
How can I know God?There are other promises (Edenic, Adamic, for example) that are never elsewhere referred to as covenants, so I simply consider them promises.
The distinction in terminology does not have significant implications, but it is always better to be precise where the text gives us the clarity to draw precise distinctions.