Hello Card
The point of the No Advertise community is that you can advertise a prefix to you iBGP neighbor, but you can instruct that neighbor not to advertise it to any other neighbors downstream. The result is that R1’s neighbor (R2) learns of the prefix but R3 and R4 don’t.
If the prefix was not advertised in the first place, R2 would not know the prefix either. This is a different result than when the No Advertise option is used.
I hope this has been helpful!
Laz