One service might classify it as $1,000, others might classify it anywhere between $1k and $100k depending on their "algorithm".
Totally. According to
this mixer, it has been noticed that a "100% tainted" bitcoin mixed with a "clean" bitcoin produces a "50% risk" bitcoin. Often times, we observe centralized exchanges acquiring "tainted" coins and then deeming them "clean". These are just examples of completely subjective interpretation of money laundering "risk" they enforce.
TLDR: Results will always be inaccurate, at least until privacy is dead.
On the extreme scenario that there is zero privacy, then their software source code is neither private, so we can all see how their accuracy function works, which is the first step to devaluing it.