I think the anomaly, is that the years don't seem to add up quite right. Verse 17:5 states the king of Assyria ... "and for three years he besieged the city of Samaria" and in the ninth year, of Hoshea's reign Samaria fell. In 18:9 it states that King Shalmaneser of Assyria attacked the city of Samaria during the seventh year of King Hoshea's reign, but if you add on the three years of besiege, the fall of Samaria would be in the tenth year, not the ninth.
Of course, I'm probably wrong, since the end of his question is "... in its present location?" which might suggest that the description of Samaria's fall is out of place in Hezekiah's history. I think it is a powerful statement because it basically says "here's what happens when you're faithless and worship false gods" and then goes on to tell the rest of the story of Hezekiah and his faithfulness in the face of certain doom and ultimate validation when the angel of the Lord killed 185,000 Assyrian soldiers in the middle of the night!