Your straight-line political spectrum is absolutely correct.
The reason that it’s so hard in real life to see that straight line is related to what you say about anarchy, that “most activity described as being anarchist is actually intent on bringing about a more severe form of totalitarianism”.
In the real world there are few or no true proponents of pure anarchy and in history the only possible instances of true anarchy are temporary and local and the result of some incredible upheaval (natural disaster or war-related).
Because true anarchy is so rare as to be invisible, the anti-conservative, anti-capitalist antics of ultra-left bomb-throwers often get mis-characterized as anarchy, when in reality, as you point out, the perpetrators are actually fighting for a Supreme Totalitarianism.
Thank you - great commentary - cheers!