Holding your phone upside down isn't an interesting test. That's just the holding power of the plug. More interesting and relevant is whether you can hold the phone at an angle, which is what a dock does. This puts a lot of stress on both the connector and the phone's jack. I would expect Micro-USB to fall apart from this abuse. I'd don't know about USB-C but don't have high hopes.
USB Type C seems to be much sturdier than microUSB. The metal sleeve has tighter tolerance and larger area. Can easily hold phone upside down. Should be able to support phone by itself. Problem is more taking more force to remove from dock or cable.
