That wasnt what I claimed, in fact the opposite. I said FPTP **does** cause 2 of the choices to generally get the vast majority of votes. What it doesnt cause is the same 2 choices to be picked every time you have a vote... In other words the only thing FPTP causes is the top two choices for any year will get 95%+ of the vote, but it does not in anyway ensure the same 2 top choices from 4 years ago will be the top 2 choices this year.
Thuis GPTP does **not** cause the same two parties to stay in power, it does cause quick jumps in party favoritism without a gradual transition... In other words A: 48% B: 48% C: 4% may switch the next year to A:48% B: 4% C: 48% in the next year without seeing an incremental shift. But there is nothing about FPTP that would prevent parties from changing.
Thus yes, the idea that FPTP means the same 2 parties will remain in power is completely a conspiracy theory. The idea that it creates skewed voting results is not.