The caption highlight timing is very inaccurate. It looks like it just steps through each word on a fixed timer, rather than using timing information from the TTS engine?
Yes just fixed timer, and using browser TTS nothing fancy here on purpose - when I did some research on tiktok videos generally simpler/worse quality seemed to be better XD
In this case, static text without the highlighter would have been better. Because the timing is so far off, the highlighter interferes with reading the captions for hearing assistance.