Well... One can believe what he wanted. I will go for what AP has said simply bcos I don't find confidence in Indian's media who are notoriously good at fake news.... And unless the Indians suddenly became Popeyes or else it is unlikely that not too long ago, they are just being thrashed by the Chinese suddenly became so good in fighting... Especially when the Chinese are well fed while the Indians are half frozen. As to there are no brawl going on... I kinda don't believe in that too.
If we go with the AP story that a brawl indeed took place, but ended in more Indian troops injured than Chinese troops. Its gonna raise many more questions.
1) Sikkim is not disputed territory. Why would the PLA want to intrude into that area with men? If China wants to do any intrusion, drones would have been more suitable. There could be plausible deniability if India spots or shoots down any drone. China could say that the drone simply 'wandered' into Indian territory. Sending men over is risking brawls and captures.
2) If China did indeed want to take some piece of Sikkim. This would be quite puzzling. It would bring little geopolitical benefit for China. Though it could bring military benefits. But this would also support India's story of 'Chinese aggression'. Not very good for PR. Plus China at this time don't look like they have any appetite for starting a war.
3) Could the opposite be true? Could it be that Indian troops from Sikkim tried to cross into Chinese territory and got checked by the PLA? Plausible, but also it doesn't add up. Would India be this brazen after what they've suffered at the hands of China at Ladakh?
Maybe I'm overthinking. But having this brawl over Sikkim is quite strange. On one hand, it does not make sense for China today. On the other hand, India and China have fought in a bloody skirmish at Sikkim in 1967. It was a decisive Indian victory according to Indian and Western historians.