I actually think it's almost always #2. Think about it.
USADA allows for a fighter to avoid 2 tests per 12 month period without violation, and only Nick Diaz has had more. Jones and Anderson can afford good drugs (#1) and may/may not be using heavily (#3) but are woefully under-informed about their options (skip 2 tests per 12 months) - so #2.
Even if using heavily, a knowledgeable PED user that stands to lose out on millions of dollars if caught, is going to microdose correctly and then utilize their 2 skipped tests as their fail safe.
I'm not saying that Anderson/Jones are stupid, just that their knowledge of PED procedures, testing procedures, cycling, etc. etc. is lacking. Long term, successful, doping typically is done with the help of a support group and isn't just left to the athletes. Balco, the Russians, Armstrong, etc. all had fairly sophisticated doping programs, with multiple people involved. And of course the more involved, over time, can lead to slip ups and mistakes.
IMO both Anderson and Jones are being guided by semi-knowledgeable people, but both likely didn't follow the prescribed protocol to the "T" and that led to their failures.
One thing I do wonder (calling on
@dimspace) is how many Whereabout violations (skipped tests) they each had prior to failing their tests. I don't believe that info is made public but IMO it'd be telling about their knowledge/intelligence of PED use if they had no more available skips when they popped (i.e. they may have known they might pop but had no choice but to give the sample(s). Versus taking and failing a test that they could have skipped taking (i.e. they didn't think there was much risk in taking the test and decided not to skip it).