The validated work allows to define the scheduled work.
The Scheduled work allows to calculate the margin (work).

Consolidation of validated work (cost) can be useful to sum the project validated work from values specified in tasks.

Hint:

If you want an answer to your question, you must write it in English "unwritten rule".

"Your question must be of benefit to the majority" 😉

You have 3 consolidation methods, depending on which level you with to enter validated work.

If you have
Project1
Phase1.1
Activity1.1.1
Activity 1.1.2
Phase1.2
Activity1.2.1
Activity1.2.2
You may want to define validated work only on phase level. If consolidation is automatic, 0 values on activity level would erase Phase value.

Imagine you define
validate on Project1=40
validate on Phase1.1=10
validate on Phase1.2=20

With consolidation = NEVER, you would get
Project1 =>40
Phase1.1 => 10
Activity1.1.1 => 0 (not defined)
Activity 1.1.2 => 0 (not defined)
Phase1.2 => 20
Activity1.2.1 => 0 (not defined)
Activity1.2.2 => 0 (not defined)
=> Project value is not consolidated as sum of Phases

With consolidation = ALWAYS, you would get
Project1 =>0
Phase1.1 => 0
Activity1.1.1 => 0 (not defined)
Activity 1.1.2 => 0 (not defined)
Phase1.2 => 0
Activity1.2.1 => 0 (not defined)
Activity1.2.2 => 0 (not defined)
=> zero values at lowest levels are cnsolidate up to project

With consolidation = ONLY IF SET, you would get
Project1 => 30
Phase1.1 => 10
Activity1.1.1 => 0 (not defined)
Activity 1.1.2 => 0 (not defined)
Phase1.2 => 20
Activity1.2.1 => 0 (not defined)
Activity1.2.2 => 0 (not defined)
=> zero values at lowest levels do not overwrite non zero values at phase level
=> non zero values on phase level are consolidated on Project level : value is updated to sum of phases
=> This is my choice for consolidation 😉