I believe that missing a milestone at any point is bad. Sometimes it can cause a hell to the project and sometimes not. When it come to any project that is affected due to missing milestone it can causes company a significant loss and some knowledge to learn for future. Even when you get out of any loss or no loss at all for missing a milestone it may affect you by missing it one more time as nothing changed or lost due to that. But it may cause significant effect for missing it again in any other project. So following the protocol is important whether it is significant for any project or not.