Apple is not shy when it comes to using proprietary ports - so I don't really buy this argument.
We can look at the iPhone 7 and it's proprietary non-USB connector as clear evidence they don't mind running proprietary connectors.
There was not a single proprietary port on the old MB Pro, except for MagSafe, which isn't really even a port, but instead a power interface.
Zero.
So somehow that means Apple hates proprietary ports?
Besides, the Thunderbolt ports might as well have been proprietary given the small number of non-apple devices that used them.
Apple is not shy when it comes to using proprietary ports - so I don't really buy this argument.
We can look at the iPhone 7 and it's proprietary non-USB connector as clear evidence they don't mind running proprietary connectors.