I'm inclined to think it's a mistake in transliteration from Cantonese to Mandarin rather than any culinary variation. The proper name for sweet and sour is 甜酸 tian suan, and 咕嚕 gu lu is a Cantonese 'nickname' for this dish that has become the more common name. Moreover, the 'old fashioned' sweet and sour pork in the link in your original post is classic 咕嚕.