Is the intent behind not excommunicating a specific individual, after knowing that they are aware of the ruling, when they haven't even consulted scholars in the first place?

The point is that ignorance in subtle matters is an excuse that prevents one from being judged as an unbeliever (kafir), but it does not necessarily prevent one from sin. So, whoever is negligent in seeking knowledge when it is easily accessible is not excused. The meaning of not declaring someone an unbeliever except after knowledge is the necessity of clarifying the religious ruling to the person until the evidence is established against them and doubt is removed. If they commit the prohibited act after knowing about it, then it is disbelief (kufr).