I think this argument has been done to death, mainly because everyone has a valid point. On the one hand it is not one of the official buses dedicated to be allocated to the X21/22 constantly but on the other hand it is a Sapphire bus on a Sapphire route. Should it happen, in an ideal world, no, does it happen, yes, very regularly - hence it's existence. In conclusion it is not necessarily rare, odd or even incorrect but that doesn't mean it does not deserve any sort of significance because at the end of the day it is different to the Sapphire X21/22 buses because it does not have sub-branding.

I think we may all have to agree to disagree and ultimately it is a persons judgement as to what they class as rare or odd.