I got the impression that problems with typing have something to do with facial structure. Similiar discussions occur on this forum. There is certainly a correlation between consensus and facial structure.
1.) People with round faces have a strengthened base function. So the base function can easily be determined whereas the creative function is frequently hard to tell.
Example: Colin Powell is clearly Ti-dominant, IxTj. Hard to say if LII or LSI.
2.) People with square faces have a strengthened creative function. This frequently leads to problems with typing the temperament.
Example: Barack Obama is clearly xNFx. Temperament is hard to say.
3.) People with rectangular faces have a strengthened ignoring function. This leads to problems with the E-I-dichotomy.
4.) People with oval faces have a strengthened demonstrative function. So the 4-dimensional functions are obvious but it is hard to determine which is which. The j-p-dichotmomy is the problem here.
Examples: Jennifer Lopez (SEE or ESE), George W. Bush (LSE or SLE).