One example is the economic metric, which is most obviously flawed by viewing 'centrists'. 'Centre' should be a 50/50, exactly between left/right.
Extreme Economic Left - everything is fully state owned, no private property exists.
Exetreme Economic Right - nothing is state owned, only private property exists.
Centre on the graph is located exactly between extreme left/right (this represents 'centrists'), therefore should represent individuals that believe in a 50:50 state owned/private property and economy. Ie through two extreme opposing views or two centre views etc.
But... How many 'centrists' by the Political Compass metric believe 50% of property rights and/or economy should be state-owned?... None.
Why does this matter? Unfortunately, PC has become the most common categorisation of political beliefs. And this categorisation represents a major (biased) frame shift along the X-axis toward right-wing economics. Where 'right-wing' becomes centrist (or normal): mild left positions look more extreme, right positions look less extreme.
Wondering why Hitler keeps appearing as a 'centrist' on r/PCM? - no he didn't roll over to the centre in his grave. Its revisionist and it was always meant to be. Let's never pretend the PC isn't pure revisionism.
It's seriously one of the worst things the internet has managed to spawn so far.