Because it feeds conspiracy theories and because there's no evidence for it? Also, let's talk DeepSeek in particular, not "China".
Looking back on the article, it is indeed using "distillation" as a special/"term of art" but not using it correctly. IE, it's not actually speculating that DeepSeek obtained OpenAI's weights and distilled them down but rather that it used OpenAI's answers/output as a starting point (which there is a different method/"term of art").
Seems reasonable they would be investing heavily in plaing state assets within OpenAI so they can copy the models.