This is different from the Malaysian dry wantan mee. The Hong Kong version is a soup, the noodles are thin and alkaline, and the wontons are shrimp heavy. At 450 calories for a full cha chaan teng bowl it is one of the lighter noodle dishes in the city, well under beef brisket noodles (550) and nowhere near a plate of fried beef ho fun (970). Fat is only 14g and most of that is the pork in the wontons.
The classic wonton shop bowl is small on purpose. A 細蓉 at the famous places in Central is maybe 250g of food with 4 wontons and a tight nest of noodles, and that lands near 300 calories. The 630g bowl CFS tested is what you get at a cha chaan teng or a noodle chain, with nearly double the noodles. So the same dish can be 300 or 450 depending on where you sit down, and the price gap is about HK$10.
The sodium is the catch, as with every Hong Kong soup noodle. CFS found 2,900mg in the full bowl, which is well over the 2,000mg daily limit. The broth is made with dried flounder and shrimp shells and it is heavily salted, so it tastes better than it is for you. The noodles themselves are around 190 calories per bowl; the wontons about 35 to 40 each; the soup adds almost nothing except salt.