Some tier commissions are not generated. Why?

Let's say in a campaign we have the general commission settings the following way:
1st tier: 5%
2nd tier: 1%
3rd tier: 1%
4th tier: 1%
 
and in the same campaign let's have a commission group (CG1) where the following commission setting can be found:
1st tier: 10%
 
 
Let's have the following affiliates: John > Peter > Jack > Samuel,  while John referred Peter, Peter referred Jack, Jack referred Samuel.
 
Now let's examine 2 cases when Samuel refers a sale, so in this case, Jack is the 2nd tier, Peter the 3rd tier and John the 4th tier.
 
Case1 - every affiliate is in the general commission group:
Samuel refers a sale, so the following commissions will be generated:
 
1st tier for Samuel
2nd tier for Jack
3rd tier for Peter
4th tier for John
 
Case2 - Jack is in the commission group named CG1
Samuel refers a sale, so the following commissions will be generated:
 
1st tier for Samuel
3rd tier for Peter
4th tier for John
 
Where is the 2nd tier commission?  Well, since Jack is in a commission group where there is no 2nd tier commission defined, therefore no 2nd tier commission was generated in this case.