In China there in the Great Firewall which blocks i.e. youtube. Fortunately in my university in China someway they provide access to youtube, so students can use youtube by means of campus wifi. I noticed on macOS I have to keep IPv6 configured to Automativally so it works (I can access youtube) most of the times.
Sometimes (very frequently) even with that configuration I cannot open youtube. I also noticed my Windows friends has much less of this problem, in Windows youtube works almost always.
Then I tried to run Windows 7 on a parallels virtual machine on macOS and bingo. Chrome in the vm loads youtube nicely.
On macOS host I tried Safari/Chrome/Firefox and none of them loads youtube.
How can this be explained?
I'll mention that I need to login to the wifi via captive portal, not sure if that matters.