The doc page "Blocks for Which Sample Time is Not Recommended" has a section "Appropriate Bocks for the Sample Time Parameter" that says "Specify sample time ... in blocks designed to model rate transtions. Examples include: .... Blocks in the Discrete Library"
However, not all blocks in the Discrete Library have a Sample Time parameter, such as Difference, Transfer Fcn First Order, and Transfer Fcn Lead or Lag,
Why do those blocks not have a Sample Time parameter like the others?