With all due respect, you are missing the point. The MSS would have access to ByteDance / TikTok data (since the mid-2010s, under the terms of Chinese laws passed at the time, though in fact the MSS almost certainly had such access--or could demand it of the company--well before those laws came into effect).

This would give the MSS a potential treasure trove of data in the context of subsequent operations designed to gather information (and 'kompromat') about specific US and other foreign government officials who had, in their previous lives, posted potentially compromising content on TikTok.

Without, BTW, resort to warrants or independent review.