hi goodguy - i am sure you are asking this question because you probably feel that you will not be able to make the 120 day timeline if you wait for ur PCC .
In such a case, pls go ahead and explain the missing PCC in your covering letter .
If you have applied for a PCC through the RPO in India , you can even attach a receipt as proof that you have applied for PCC. They will definitely consider the case.
I did the same ; and sent my PCC later when i received it.
All my other docs honoured the 120 timeline and the PCC followed later on.
So far, it has had no adverse effect on my processing timelines,etc. But if you can afford to wait a bit more (before your 120 day timeline) for your PCC to arrive , then that would be ideal!
Hope this helps.