SCD 4 confusion

Hi Guys,
can someone describe me what is a type 4 scd is? Looks like Kimball group definition doesn't match other definitions in the market.
Kimball, describes it as a mini dimension which is used to remove volatile attributes of a type 2 dimension in a separate table and attach it directly to the fact with FK-PK
Other definition for SCD4 is having a type 1 SCD for actual values and keeping the history attached to the type1, which looks kind of outrigger.
Which one is SCD4? Are there lack of numbers in universe that they use same number with different descriptions?? :))

By the way,
Anybody used the solution of SCD 1 with connected history table to it? I wonder is there any performance issue with such design in a system where most of the SQLs are retrieving actual values of dimensions and very less of them might need to see the exact dimension value in a given time.

Thanks!