Sharing cart among sales channels

Cart can be shared among sales channels even if products not available for particular sales channel, is it bug or feature? If it’s a feature, what is the purpose?

How to reproduce (checked on v6.4.11.1):

Add product to cart on sales channel A.
Create sales channel B.
Go to sales channel B cart, I see product added on sales channel A, BUT I cannot open product for this sales channel, because it wasn’t assigned.
I’m able to successfully place the order for sales channel B.