IQ, among its myriad problems, is not an absolute measure. It's a comparison to "Average".
A 100 IQ from 1800 is not the same as a 100 IQ from 2018.
The IQ points above and below 100 are based on deviation from the mean. So, for example, by definition there can only be like 10 or so people with 180 IQ, if there were more then the average would change and they would no longer be 180 IQ.
On top of that, the further you get from 100, the less certain the test is. It's pretty fucking terrible at the margins. So this means a couple things. Firstly, anyone bragging about a 200+ IQ is completely full of shit, that's like saying they use more than 100% of their brain or something. Secondly, even if someone got a "high IQ score" one time, that number isn't their IQ anymore, both because the scores are re-normalized, and the person's brain changes.