Yes and no.
TikTok SEO in of itself using target keywords in hashtags is not really going to move the needle.
A lot of people played around with this, and I'm sure you can look up old threads of people saying that this stuff doesn't work.
It doesn't on its face, but it does work in a roundabout way.
When you use hashtags as well as keyword-crafted titles, you are more likely to attract the eyeballs of people who are really interested in certain niches.
If you attract enough of these people, TikTok will start to classify your content along the lines of the interests of people who fit the profile of the niche-interested people.
Do you understand where I am coming from?
I hope this is not confusing.
Facebook used to operate this way, but they kind of dropped the ball.
TikTok mastered this.
You have to understand that TikTok seems to magically read people's minds in terms of niche selection because of user profiling.
They don't profile people individually so that the information is personally identifiable.
Instead, they put people in terms of "niche clusters."
A person who is interested in a niche would be looking for certain criteria, and this can be tied to hashtags and certain types of videos and then it goes on from there.
To top it all off, TikTok uses an automated learning system so it makes a lot of guesses based on categories, and it will verify if those guesses are correct based on actual user behavior.