Or it could be that English is complex and words can mean many things. Just stealing from Meriam Webster here:
3 : something established by authority, custom, or general consent as a model or example : criterion quite slow by today’s standards
4 : something set up and established by authority as a rule for the measure of quantity, weight, extent, value, or quality
By means of 3, micro-HDMI is not standard as they are not in common use by general consent. But there is a ‘standards’ organization which authorizes them, so it meets definition 4.
It was pretty darn clear that @Lanthade meant the “by general consent” definition. And by that meaning, micro-HDMI connectors are certainly non-standard. They probably amount to a low single digit percent of all HDMI connectors. And they probably have an even smaller use rate than the full sized connector. That meaning that if you find a device with such a connector on it, the full sized connector is way more likely to actually be plugged into something.
If we want to go full up pedant like @agies seems to want to, then there isn’t a connector named micro-HDMI. It’s an HDMI v1.4 Type-D connector.