I might be missing something, but I don't see the relevance of discovery when TikTok is suing the US government. The government will need to establish that it followed due process in drafting and executing the executive order. I can't see what relevant information TikTok would hold about that? Posisbly they would have correspondence between the government and themselves, but you would expect the government to have copies of that too. It may be that the order was carried out because of TikTok's behaviour, but that would need to be behaviour that the government has documentation of, so it wouldn't come through discovery.
Also, just to be clear, this law suit isn't going to be litigated by Chinese lawyers, the lawyers are going to be US lawyers who have to adhere to the US standards. If they think that TikTok is failing to provide something to the court or are acting unethically they are obligated to tell the court of be disbared.
DoJ could ask ByteDance for information about TikTok US data security. It's a no brainer to see why DoJ proving this issue would be hard if the laws were stringent, but it doesn't seem like his entity list (if that's what he's using) power has any restrictions on Chinese foreign commerce - historically it's been interpreted as very broad, so as far as SCOTUS will let him.
Also, just to be clear, this law suit isn't going to be litigated by Chinese lawyers, the lawyers are going to be US lawyers who have to adhere to the US standards. If they think that TikTok is failing to provide something to the court or are acting unethically they are obligated to tell the court of be disbared.