In Dushwaresque manner - I ask what is right

Re: In Dushwaresque manner - I ask what is right

Parallel vs Series

In PERT which is a critical path analysis, one needs to create a string of parallel and serial activies, such that work duration can be minimised/simplified.

For parallel activities the first statement will be more relevant for serial activities the latter statement will be more relevant.

Are there any exceptions to this that you can cite based on the newer condition of this comparison?