I noted that to make the sound the sides of the tongue make an occlusion in the laterals, this would mean the point of greatest constriction isn't just in the alveolar ridge.
As aml has pointed out in the comments, a stop consonant involves stopping the airflow entirely (hence the name). For stops made using the tongue, this means the tongue needs to block off the entire mouth, so there will always be contact both along the sides and in the middle.
Since the sides of the tongue do pretty much the same thing in an alveolar stop versus a palatal stop versus a dental stop, we choose to ignore them: they simply don't give us any useful information. Instead we focus on where the tip of the tongue is, since that varies more and is much easier to measure. That's what determines the "official" place of articulation.