Why Do Some Blocks in the Discrecte Library Not Have a Sample Time Parameter?

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?

Answer 1

[Jonas]

The discrete blocks you mention inherit their sample time from the blocks they are connected to. The Difference block for example, uses the current sample and the previous sample, but the sample rate is inherited by other blocks.

[Paul]

But why are those blocks different from the others where the Sample Time is a block parameter. Why shouldn't the user be able to specify a sample time for the Difference block, for example?

[Jonas]

I do not know the reason why in some blocks you can specify the sampling time and in others it is implicit. If you want to specify a sampling time just for one block where it is implicit, you can use the Rate Transition block before and after. So it is not really a limitation, just a matter of convenience.