ByteDance's Douyin product has Chinese employees that are based in China. TikTok employees are also ByteDance employees which means a ByteDance employee that passes through their "strict controls" can access whatever TikTok data they want. Even if that's a dozen Chinese nationals that can get access that's a dozen people required by Chinese law to help the state security aparatus.
I don't see any reason to give them the benefit of the doubt considering they already moderate content the Chinese government doesn't like [0] as a matter of company policy.